The endometrial transcriptome of infertile women with and without implantation failure

INTRODUCTION

Implantation failure after transferring morphologically "good-quality" embryos in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) may be explained by impaired endometrial receptivity. Analyzing the endometrial transcriptome analysis may reveal the underlying processes and could help in guiding prognosis and using targeted interventions for infertility. This exploratory study investigated whether the endometrial transcriptome profile was associated with short-term or long-term implantation outcomes (ie success or failure).

MATERIAL AND METHODS

Mid-luteal phase endometrial biopsies of 107 infertile women with one full failed IVF/ICSI cycle, obtained within an endometrial scratching trial, were subjected to RNA-sequencing and differentially expressed genes analysis with covariate adjustment (age, body mass index, luteinizing hormone [LH]-day). Endometrial transcriptomes were compared between implantation failure and success groups in the short term (after the second fresh IVF/ICSI cycle) and long term (including all fresh and frozen cycles within 12 months). The short-term analysis included 85/107 women (33 ongoing pregnancy vs 52 no pregnancy), excluding 22/107 women. The long-term analysis included 46/107 women (23 'fertile' group, ie infertile women with a live birth after ≤3 embryos transferred vs 23 recurrent implantation failure group, ie no live birth after ≥3 good quality embryos transferred), excluding 61/107 women not fitting these categories. As both analyses drew from the same pool of 107 samples, there was some sample overlap. Additionally, cell type enrichment scores and endometrial receptivity were analyzed, and an endometrial development pseudo-timeline was constructed to estimate transcriptomic deviations from the optimum receptivity day (LH + 7), denoted as ΔWOI (window of implantation).

RESULTS

There were no significantly differentially expressed genes between implantation failure and success groups in either the short-term or long-term analyses. Principal component analysis initially showed two clusters in the long-term analysis, unrelated to clinical phenotype and no longer distinct following covariate adjustment. Cell type enrichment scores did not differ significantly between groups in both analyses. However, endometrial receptivity analysis demonstrated a potentially significant displacement of the WOI in the non-pregnant group compared with the ongoing pregnant group in the short-term analysis.

CONCLUSIONS

No distinct endometrial transcriptome profile was associated with either implantation failure or success in infertile women. However, there may be differences in the extent to which the WOI is displaced.

Clinical outcomes from ART in predicted hyperresponders: in vitro maturation of oocytes versus conventional ovarian stimulation for IVF/ICSI

STUDY QUESTION

Do ongoing pregnancy rates (OPRs) differ in predicted hyperresponders undergoing ART after IVM of oocytes compared with conventional ovarian stimulation (OS) for IVF/ICSI?

SUMMARY ANSWER

One cycle of IVM is non-inferior to one cycle of OS in women with serum anti-Müllerian hormone (AMH) levels ≥10 ng/ml.

WHAT IS KNOWN ALREADY

Women with high antral follicle count and elevated serum AMH levels, indicating an increased functional ovarian reserve, are prone to hyperresponse during ART treatment. To avoid iatrogenic complications of OS, IVM has been proposed as a mild-approach alternative treatment in predicted hyperresponders, including women with polycystic ovary syndrome (PCOS) who are eligible for ART. To date, inferior pregnancy rates from IVM compared to OS have hampered the uptake of IVM by ART clinics. However, it is unclear whether the efficiency gap between IVM and OS may differ depending on the extent of AMH elevation.

STUDY DESIGN, SIZE, DURATION

This study is a retrospective cohort analysis of clinical and laboratory data from the first completed highly purified hMG (HP-hMG) primed, non-hCG-triggered IVM or OS (FSH or HP-hMG stimulation in a GnRH antagonist protocol) cycle with ICSI in predicted hyperresponders ≤36 years of age at a tertiary referral university hospital. A total of 1707 cycles were included between January 2016 and June 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Predicted hyperresponse was defined as a serum AMH level ≥3.25 ng/ml (Elecsys® AMH, Roche Diagnostics). The primary outcome was cumulative ongoing pregnancy rate assessed 10-11 weeks after embryo transfer (ET). The predefined non-inferiority limit was -10.0%. The analysis was adjusted for AMH strata. Time-to-pregnancy, defined as the number of ET cycles until ongoing pregnancy was achieved, was a secondary outcome. Statistical analysis was performed using a multivariable regression model controlling for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Data from 463 IVM cycles were compared with those from 1244 OS cycles. Women in the IVM group more often had a diagnosis of Rotterdam PCOS (434/463, 93.7%) compared to those undergoing OS (522/1193, 43.8%), were significantly younger (29.5 years versus 30.5 years, P ≤ 0.001), had a higher BMI (25.7 kg/m2 versus 25.1 kg/m2, P ≤ 0.01) and higher AMH (11.6 ng/ml versus 5.3 ng/ml, P ≤ 0.001). Although IVM cycles yielded more cumulus-oocyte complexes (COCs) (24.5 versus 15.0 COC, P ≤ 0.001), both groups had similar numbers of mature oocytes (metaphase II (MII)) (11.9 MII versus 10.6 MII, P = 0.9). In the entire cohort, non-adjusted cumulative OPR from IVM was significantly lower (198/463, 42.8%) compared to OS (794/1244, 63.8%), P ≤ 0.001. When analysing OPR across different serum AMH strata, cumulative OPR in both groups converged with increasing serum AMH, and OPR from IVM was non-inferior compared to OS from serum AMH levels >10 ng/ml onwards (113/221, 51.1% (IVM); 29/48, 60.4% (OS)). The number of ETs needed to reach an ongoing pregnancy was comparable in both the IVM and the OS group (1.6 versus 1.5 ET's, P = 0.44). Multivariable regression analysis adjusting for ART type, age, BMI, oocyte number, and PCOS phenotype showed that the number of COCs was the only parameter associated with OPR in predicted hyperresponders with a serum AMH >10 ng/ml.

LIMITATIONS, REASONS FOR CAUTION

These data should be interpreted with caution as the retrospective nature of the study holds the possibility of unmeasured confounding factors.

WIDER IMPLICATIONS OF THE FINDINGS

Among subfertile women who are eligible for ART, IVM, and OS resulted in comparable reproductive outcomes in a subset of women with a serum AMH ≥10 ng/ml. These findings should be corroborated by a randomised controlled trial (RCT) comparing both treatments in selected patients with elevated AMH.

STUDY FUNDING/COMPETING INTEREST(S)

There was no external funding for this study. P.D. has been consultant to Merck Healthcare KGaA (Darmstadt, Germany) from April 2021 till June 2023 and is a Merck employee (Medical Director, Global Medical Affairs Fertility) with Merck Healthcare KGAaA (Darmstadt, Germany) since July 2023. He declares honoraria for lecturing from Merck KGaA, MSD, Organon, and Ferring. The remaining authors declared no conflict of interest pertaining to this study.

TRIAL REGISTRATION NUMBER

N/A.

Does dual oocyte retrieval with continuous FSH administration increase the number of mature oocytes in low responders? An open-label randomized controlled trial

STUDY QUESTION

Is there an increase in the total number of metaphase II (MII) oocytes between a conventional ovarian stimulation (OS) and a double uninterrupted stimulation?

SUMMARY ANSWER

There is no increase in the total number of MII oocytes when comparing one conventional OS to a continuous stimulation with double oocyte aspiration.

WHAT IS KNOWN ALREADY

Based on the concept of multiple follicular waves, the combination of two stimulations in the same ovarian cycle has gained interest in patients with a low ovarian reserve. This so-called dual stimulation approach is usually characterized by a discontinuation of FSH administration for ∼5 days and appears to have a favourable impact on the number of retrieved oocytes without affecting the embryo quality or ploidy status. The outcomes of dual uninterrupted OS have not yet been studied.

STUDY DESIGN, SIZE, DURATION

This was an open-label randomized controlled trial (RCT) with superiority design, performed in a single tertiary centre. Subjects were randomized with a 1:1 allocation into two groups between October 2019 and September 2021. All patients underwent a conventional stimulation with recombinant FSH. When two or more follicles of 17 mm were present, the final inclusion criterion was assessed; randomization occurred only in the presence of ≤9 follicles of ≥11 mm. In Group A, ovulation was triggered with hCG, and oocyte retrieval (OR) was performed 34-36 h later, followed by a fresh single or double embryo transfer (SET or DET) on Day 3/5. In Group B, ovulation was triggered with GnRH agonist, followed by another OS, without discontinuation of the FSH administration. In the presence of one or more follicles of ≥17 mm, the second stimulation was completed with hCG. A freeze-all strategy (Day 3/5) was applied for both retrievals, followed by transfer of one or two embryos in an artificially prepared frozen-thawed cycle. In the absence of one or more follicles of ≥17 mm after 13 additional days of stimulation, the second cycle was cancelled. All ORs were executed by a senior fertility specialist who was blinded for the first treatment, and all follicles >10 mm were aspirated, according to routine clinical practice. The primary outcome was the total number of MII oocytes. Patients were followed up until all embryos were transferred, or until live birth was achieved. Other secondary outcomes included the number of cumulus-oocyte complexes (COCs), the number of good quality embryos (Day 3/5), the ongoing pregnancy rate, and gonadotropin consumption.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients between 25 and 40 years old, with an anti-Müllerian hormone level of ≤1.5 ng/ml, antral follicle count of ≤6, or ≤5 oocytes after a previous stimulation, were included. At the start, 70 patients were eligible for participation in the trial, of whom 48 patients fulfilled the final inclusion criterium and were randomized. After drop-out of two patients, 23 patients were randomized to a single round of OS (Group A), and 23 patients were randomized to two uninterrupted rounds of OS (Group B).

MAIN RESULTS AND THE ROLE OF CHANCE

Baseline characteristics were similar between both groups. The cumulative number of COCs and MII oocytes after completion of the second OR was similar in Group A and Group B [5.3 ± 2.7 versus 5.3 ± 3.0 (P = 0.95); 4.1 ± 2.4 versus 4.3 ± 2.7 (P = 0.77)]. Likewise, a comparable number of excellent and good quality embryos was available on Day 3 (3.0 ± 2.0 versus 2.7 ± 2.0; P = 0.63). In Group B, the cancellation rate due to insufficient response to the second round of stimulation was 39.1% (9/23). When focusing on the first stimulation in both groups, there were no significant differences regarding basal FSH, gonadotropin consumption, and the number of preovulatory follicles. After the first OR, the mean number of COC and MII oocytes was significantly higher in Group A (who had hCG triggering), compared to Group B (who had GnRH agonist triggering) [5.3 ± 2.7 versus 3.3 ± 2.2; difference 95% CI (0.54 to 3.45), P = 0.004 and 4.1 ± 2.4 versus 3.0 ± 2.2; difference 95% CI (-0.15 to 2.6), P = 0.05, respectively]. Likewise, the number of excellent and good quality embryos on Day 3 was significantly higher (3.0 ± 2.0 versus 1.9 ± 1.7; P = 0.02) in Group A.

LIMITATIONS, REASONS FOR CAUTION

This study was powered to demonstrate superiority for the number of MII oocytes after dual stimulation. Investigating the impact of dual stimulation on pregnancy rates would have required a larger sample size. Furthermore, the heterogeneity in embryo vitrification and transfer policies precluded a correct comparison of embryologic outcomes between both groups.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first RCT investigating the role of continuous stimulation with double aspiration in low responders. Our results show no statistically significant differences in the cumulative number of MII oocytes between one conventional stimulation with fresh ET and two consecutive stimulations with a freeze-only approach. Furthermore, the observed suboptimal oocyte yield after agonist ovulation triggering in low responders in the dual uninterrupted OS group is a reason for concern and further scrutiny, given that previous RCTs have shown similar outcomes in normal and high responders after hCG and GnRH agonist triggers.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by a research grant from Organon. H.T. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, Cook, Goodlife, and Ferring. L.B. received fees for lectures from Merck & Organon and support for attending ESHRE 2023. M.D.V. reports fees for lectures from Ferring, Merck, Organon, IBSA, Gedeon Richter, and Cooper Surgical and support for attending ASRM 2023. S.M. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, IBSA, and Merck. C.B. was on the Advisory board and received consulting fees from Theramex and received honoraria for lectures and presentations from Abbott, Ferring, Gedeon-Richter, IBSA, and Merck.

TRIAL REGISTRATION NUMBER

NCT03846544.

TRIAL REGISTRATION DATE

19 February 2019.

DATE OF FIRST PATIENT’S ENROLMENT

28 October 2019.

Oral dydrogesterone versus micronized vaginal progesterone for luteal phase support: a double-blind crossover study investigating pharmacokinetics and impact on the endometrium

STUDY QUESTION

How do plasma progesterone (P) and dydrogesterone (D) concentrations together with endometrial histology, transcriptomic signatures, and immune cell composition differ when oral dydrogesterone (O-DYD) or micronized vaginal progesterone (MVP) is used for luteal phase support (LPS)?

SUMMARY ANSWER

Although after O-DYD intake, even at steady-state, plasma D and 20αdihydrodydrogesterone (DHD) concentrations spiked in comparison to P concentrations, a similar endometrial signature was observed by histological and transcriptomic analysis of the endometrium.

WHAT IS KNOWN ALREADY

O-DYD for LPS has been proven to be noninferior compared to MVP in two phase III randomized controlled trials. Additionally, a combined individual participant data and aggregate data meta-analysis indicated that a higher pregnancy rate and live birth rate may be obtained in women receiving O-DYD versus MVP for LPS in fresh IVF/ICSI cycles. Little data are available on the pharmacokinetic (PK) profiles of O-DYD versus MVP and their potential molecular differences at the level of the reproductive organs, particularly at the endometrial level.

STUDY DESIGN, SIZE, DURATION

Thirty oocyte donors were planned to undergo two ovarian stimulation (OS) cycles with dual triggering (1.000 IU hCG + 0.2 mg triptorelin), each followed by 1 week of LPS: O-DYD or MVP, in a randomized, cross-over, double-blind, double-dummy fashion. On both the first and eighth days of LPS, serial blood samples upon first dosing were harvested for plasma D, DHD, and P concentration analyses. On Day 8 of LPS, an endometrial biopsy was collected for histologic examination, transcriptomics, and immune cell analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All oocyte donors were <35 years old, had regular menstrual cycles, no intrauterine contraceptive device, anti-Müllerian hormone within normal range and a BMI ≤29 kg/m2. OS was performed on a GnRH antagonist protocol followed by dual triggering (1.000 IU hCG + 0.2 mg triptorelin) as soon as ≥3 follicles of 20 mm were present. Following oocyte retrieval, subjects initiated LPS consisting of MVP 200 mg or O-DYD 10 mg, both three times daily. D, DHD, and P plasma levels were measured using liquid chromatography-tandem mass spectrometry. Histological assessment was carried out using the Noyes criteria. Endometrial RNA-sequencing was performed for individual biopsies and differential gene expression was analyzed. Endometrial single-cell suspensions were created followed by flow cytometry for immune cell typing.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 21 women completed the entire study protocol. Subjects and stimulation characteristics were found to be similar between groups. Following the first dose of O-DYD, the average observed maximal plasma concentrations (Cmax) for D and DHD were 2.9 and 77 ng/ml, respectively. The Cmax for D and DHD was reached after 1.5 and 1.6 h (=Tmax), respectively. On the eighth day of LPS, the first administration of that day gave rise to a Cmax of 3.6 and 88 ng/ml for D and DHD, respectively. For both, the observed Tmax was 1.5 h. Following the first dose of MVP, the Cmax for P was 16 ng/ml with a Tmax of 4.2 h. On the eighth day of LPS, the first administration of that day showed a Cmax for P of 21 ng/ml with a Tmax of 7.3 h. All 42 biopsies showed endometrium in the secretory phase. The mean cycle day was 23.9 (±1.2) in the O-DYD group versus 24.0 (±1.3) in the MVP group. RNA-sequencing did not reveal significantly differentially expressed genes between samples of both study groups. The average Euclidean distance between samples following O-DYD was significantly lower than following MVP (respectively 12.1 versus 18.8, Mann-Whitney P = 6.98e-14). Immune cell profiling showed a decrease of CD3 T-cell, γδ T-cell, and B-cell frequencies after MVP treatment compared to O-DYD, while the frequency of natural killer (NK) cells was significantly increased.

LIMITATIONS, REASONS FOR CAUTION

The main reason for caution is the small sample size, given the basic research nature of the project. The plasma concentrations are best estimates as this was not a formal PK study. Whole tissue bulk RNA-sequencing has been performed not correcting for bias caused by different tissue compositions across biopsies.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study comparing O-DYD/MVP, head-to-head, in a randomized design on a molecular level in IVF/ICSI. Plasma serum concentrations suggest that administration frequency is important, in addition to dose, specifically for O-DYD showing a rapid clearance. The molecular endometrial data are overall comparable and thus support the previously reported noninferior reproductive outcomes for O-DYD as compared to MVP. Further research is needed to explore the smaller intersample distance following O-DYD and the subtle changes detected in endometrial immune cells.

STUDY FUNDING/COMPETING INTEREST(S)

Not related to this work, C.Bl. has received honoraria for lectures, presentations, manuscript writing, educational events, or scientific advice from Abbott, Ferring, Organon, Cooper Surgical, Gedeon-Richter, IBSA, and Merck. H.T. has received honoraria for lectures, presentations, manuscript writing, educational events, or scientific advice from Abbott, Ferring, Cooper Surgical, Gedeon-Richter, Cook, and Goodlife. S.M. has received honoraria for lectures, presentations, educational events, or scientific advice from Abbott, Cooper Surgical, Gedeon-Richter, IBSA, and Merck and Oxolife. G.G. has received honoraria for lectures, presentations, educational events, or scientific advice from Merck, MSD, Organon, Ferring, Theramex, Gedeon-Richter, Abbott, Biosilu, ReprodWissen, Obseva, PregLem, Guerbet, Cooper, Igyxos, and OxoLife. S.V.-S. is listed as inventor on two patents (WO2019115755A1 and WO2022073973A1), which are not related to this work.

TRIAL REGISTRATION NUMBER

EUDRACT 2018-000105-23.

An unbiased approach of molecular characterization of the endometrium: toward defining endometrial-based infertility

Infertility is a complex condition affecting millions of couples worldwide. The current definition of infertility, based on clinical criteria, fails to account for the molecular and cellular changes that may occur during the development of infertility. Recent advancements in sequencing technology and single-cell analysis offer new opportunities to gain a deeper understanding of these changes. The endometrium has a potential role in infertility and has been extensively studied to identify gene expression profiles associated with (impaired) endometrial receptivity. However, limited overlap among studies hampers the identification of relevant downstream pathways that could play a role in the development of endometrial-related infertility. To address these challenges, we propose sequencing the endometrial transcriptome of healthy and infertile women at the single-cell level to consistently identify molecular signatures. Establishing consensus on physiological patterns in endometrial samples can aid in identifying deviations in infertile patients. A similar strategy has been used with great success in cancer research. However, large collaborative initiatives, international uniform protocols of sample collection and processing are crucial to ensure reliability and reproducibility. Overall, the proposed approach holds promise for an objective and accurate classification of endometrial-based infertility and has the potential to improve diagnosis and treatment outcomes.

Circadian serum progesterone variations on the day of frozen embryo transfer in artificially prepared cycles

RESEARCH QUESTION

What is the intra-day variation of serum progesterone related to vaginal progesterone administration on the day of frozen embryo transfer (FET) in an artificial cycle?

DESIGN

A prospective cohort study was conducted including 22 patients undergoing a single blastocyst artificial cycle (AC)-FET from August to December 2022. Endometrial preparation was achieved by administering oestradiol valerate (2 mg three times daily) and consecutively micronized vaginal progesterone (MVP; 400 mg twice daily). A blastocyst FET was performed on the 6th day of MVP administration. Serum progesterone concentrations were measured on the day of transfer at 08:00, 12:00, 16:00 and 20:00 hours. The first and last blood samples were collected just before MVP was administered.

RESULTS

The mean age and body mass index of the study population were 33.95 ± 3.98 years and 23.10 ± 1.95 kg/m2. The mean P-values at 08:00, 12:00, 16:00 and 20:00 hours were 11.72 ± 4.99, 13.59 ± 6.33, 10.23 ± 3.81 and 9.28 ± 3.09 ng/ml, respectively. A significant decline, of 2.41 ng/ml (95% confidence interval 0.81-4.00), was found between the first and last progesterone measurements.

CONCLUSION

A statistically significant intra-day variation of serum progesterone concentrations on the day of FET in artificially prepared cycles was observed. This highlights the importance of a standardized procedure for the timing of progesterone measurement on the day of AC-FET. Of note, the study results are applicable only to women using MVP for luteal phase support; therefore it is necessary to confirm its validity in comparison with the different existing administration routes of progesterone.

IVF with reception of oocytes from partner in lesbian couples: a systematic review and SWOT analysis

The growing utilization of assisted reproductive technology (ART) by the LGBTQ+ community, especially among lesbian couples, challenges societal norms and promotes inclusivity. The reception of oocytes from partner (ROPA) technique enables both female partners to have a biological connection to their child. A systematic review was conducted of the literature on ROPA IVF to provide the latest data and a SWOT analysis was subsequently performed to understand the strengths, weaknesses, opportunities and threats associated with ROPA IVF. Publications from 2000 to 2023 with relevant keywords were reviewed and 16 records were included. Five studies provided clinical information on couples who used ROPA IVF. ROPA IVF provides a unique opportunity for a biological connection between the child and both female partners and addresses concerns related to oocyte donation and anonymity. Weaknesses include limited cost-effectiveness data and unresolved practical implications. Opportunities lie in involving both partners in parenthood, advancing ART success rates and mitigating risks. Threats encompass increased pregnancy complications, ethical concerns, insufficient safety data, legal or cultural barriers, and emotional stress. In conclusion, ROPA IVF offers a promising solution for lesbian couples seeking to create a family in which both partners want to establish a biological connection with their child.

Progestin primed ovarian stimulation using dydrogesterone from day 7 of the cycle onwards in oocyte donation cycles: a longitudinal study

RESEARCH QUESTION

Does a progestin-primed ovarian stimulation (PPOS) protocol with dydrogesterone from cycle day 7 yield similar outcomes compared with a gonadotrophin-releasing hormone (GnRH) antagonist protocol in the same oocyte donors?

DESIGN

This retrospective longitudinal study included 128 cycles from 64 oocyte donors. All oocyte donors had the same type of gonadotrophin and daily dose in both stimulation cycles. The primary outcome was the number of cumulus-oocyte complexes (COC) retrieved.

RESULTS

The number of COC retrieved (mean ± SD 19.7 ± 10.8 versus 19.2 ± 8.3; P = 0.5) and the number of metaphase II oocytes (15.5 ± 8.4 versus 16.2 ± 7.0; P = 0.19) were similar for the PPOS and GnRH antagonist protocols, respectively. The duration of stimulation (10.5 ± 1.5 days versus 10.8 ± 1.5 days; P = 0.14) and consumption of gonadotrophins (2271.9 ± 429.7 IU versus 2321.5 ± 403.4 IU; P = 0.2) were also comparable, without any cases of premature ovulation. Nevertheless, there was a significant difference in the total cost of medication per cycle: €898.3 ± 169.9 for the PPOS protocol versus €1196.4 ± 207.5 (P < 0.001) for the GnRH antagonist protocol.

CONCLUSION

The number of oocytes retrieved and number of metaphase II oocytes were comparable in both stimulation protocols, with the advantage of significant cost reduction in favour of the PPOS protocol compared with the GnRH antagonist protocol. No cases of premature ovulation were observed, even when progestin was started later in the stimulation.

Endometrial scratching in women undergoing IVF/ICSI: an individual participant data meta-analysis

BACKGROUND

In IVF/ICSI treatment, the process of embryo implantation is the success rate-limiting step. Endometrial scratching has been suggested to improve this process, but it is unclear if this procedure increases the chance of implantation and live birth (LB) and, if so, for whom, and how the scratch should be performed.

OBJECTIVE AND RATIONALE

This individual participant data meta-analysis (IPD-MA) aims to answer the question of whether endometrial scratching in women undergoing IVF/ICSI influences the chance of a LB, and whether this effect is different in specific subgroups of women. After its incidental discovery in 2000, endometrial scratching has been suggested to improve embryo implantation. Numerous randomized controlled trials (RCTs) have been conducted, showing contradicting results. Conventional meta-analyses were limited by high within- and between-study heterogeneity, small study samples, and a high risk of bias for many of the trials. Also, the data integrity of several trials have been questioned. Thus, despite numerous RCTs and a multitude of conventional meta-analyses, no conclusion on the clinical effectiveness of endometrial scratching could be drawn. An IPD-MA approach is able to overcome many of these problems because it allows for increased uniformity of outcome definitions, can filter out studies with data integrity concerns, enables a more precise estimation of the true treatment effect thanks to adjustment for participant characteristics and not having to make the assumptions necessary in conventional meta-analyses, and because it allows for subgroup analysis.

SEARCH METHODS

A systematic literature search identified RCTs on endometrial scratching in women undergoing IVF/ICSI. Authors of eligible studies were invited to share original data for this IPD-MA. Studies were assessed for risk of bias (RoB) and integrity checks were performed. The primary outcome was LB, with a one-stage intention to treat (ITT) as the primary analysis. Secondary analyses included as treated (AT), and the subset of women that underwent an embryo transfer (AT+ET). Treatment-covariate interaction for specific participant characteristics was analyzed in AT+ET.

OUTCOMES

Out of 37 published and 15 unpublished RCTs (7690 participants), 15 RCTs (14 published, one unpublished) shared data. After data integrity checks, we included 13 RCTs (12 published, one unpublished) representing 4112 participants. RoB was evaluated as 'low' for 10/13 RCTs. The one-stage ITT analysis for scratch versus no scratch/sham showed an improvement of LB rates (odds ratio (OR) 1.29 [95% CI 1.02-1.64]). AT, AT+ET, and low-RoB-sensitivity analyses yielded similar results (OR 1.22 [95% CI 0.96-1.54]; OR 1.25 [95% CI 0.99-1.57]; OR 1.26 [95% CI 1.03-1.55], respectively). Treatment-covariate interaction analysis showed no evidence of interaction with age, number of previous failed embryo transfers, treatment type, or infertility cause.

WIDER IMPLICATIONS

This is the first meta-analysis based on IPD of more than 4000 participants, and it demonstrates that endometrial scratching may improve LB rates in women undergoing IVF/ICSI. Subgroup analysis for age, number of previous failed embryo transfers, treatment type, and infertility cause could not identify subgroups in which endometrial scratching performed better or worse. The timing of endometrial scratching may play a role in its effectiveness. The use of endometrial scratching in clinical practice should be considered with caution, meaning that patients should be properly counseled on the level of evidence and the uncertainties.

Culturomics in Unraveling the Upper Female Reproductive Tract Microbiota

In recent years, the study of the human microbiome has surged, shedding light on potential connections between microbiome composition and various diseases. One specific area of intense interest within this research is the female reproductive tract, as it holds the potential to influence the process of embryo implantation. Advanced sequencing technologies have delivered unprecedented insights into the microbial communities, also known as microbiota, residing in the female reproductive tract. However, their efficacy encounters significant challenges when analyzing low-biomass microbiota, such as those present in the endometrium. These molecular techniques are susceptible to contamination from laboratory reagents and extraction kits, leading to sequencing bias that can significantly alter the perceived taxonomy of a sample. Consequently, investigating the microbiota of the upper female reproductive tract necessitates the exploration of alternative methods. In this context, the current review delves into the application of culturomics in unraveling the upper female reproductive tract microbiota. While culturomics holds value in research, its transition to routine clinical practice appears remote, at least in the foreseeable future.

An integrative analysis of endometrial steroid metabolism and transcriptome in relation to endometrial receptivity in in vitro fertilization patients

OBJECTIVE

To study the relationship between the steroid concentration in the endometrium, in serum, and the gene expression level of steroid-metabolizing enzymes in the context of endometrial receptivity in in vitro fertilization (IVF) patients.

DESIGN

Case-control study of 40 IVF patients recruited in the SCRaTCH study (NTR5342), a randomized controlled trial investigating pregnancy outcome after "endometrial scratching." Endometrial biopsies and serum were obtained from patients with a first failed IVF cycle randomized to the endometrial scratch in the midluteal phase of the natural cycle before the next fresh embryo transfer during the second IVF cycle.

SETTING

University hopsital.

PATIENTS

Twenty women with clinical pregnancy were compared with 20 women who did not conceive after fresh embryo transfer. Cases and controls were matched for primary vs. secondary infertility, embryo quality, and age.

INTERVENTION

None.

MAIN OUTCOME MEASURE(S)

Steroid concentrations in endometrial tissue homogenates and serum were measured with liquid chromatography-mass spectrometry. The endometrial transcriptome was profiled by RNA-sequencing, followed by principal component analysis and differential expression analysis. False discovery rate-adjusted and log-fold change >|0.5| were selected as the threshold for differentially expressed genes.

RESULT(S)

Estrogen levels were comparable in both serum (n = 16) and endometrium (n = 40). Androgens and 17-hydroxyprogesterone were higher in serum than that in endometrium. Although steroid levels did not vary between pregnant and nonpregnant groups, subgroup analysis of primary women with infertility showed a significantly lower estrone concentration and estrone:androstenedione ratio in serum of the pregnant group (n = 5) compared with the nonpregnant group (n = 2). Expression of 34 out of 46 genes encoding the enzymes controlling the local steroid metabolism was detected, and estrogen receptor β gene was differentially expressed between pregnant and nonpregnant women. When only the primary infertile group was considered, 28 genes were differentially expressed between pregnant and nonpregnant women, including HSD11B2, that catalyzes the conversion of cortisol into cortisone.

CONCLUSION(S)

Steroidomic and transcriptomic analyses show that steroid concentrations are regulated by the local metabolism in the endometrium. Although no differences were found in endometrial steroid concentration in the pregnant and nonpregnant IVF patients, primary women with infertility showed deviations in steroid levels and gene expression, indicating that a more homogeneous patient group is required to uncover the exact role of steroid metabolism in endometrial receptivity.

CLINICAL TRIAL REGISTRATION NUMBER

The study was registered in the Dutch trial registry (www.trialregister.nl), registration number NL5193/NTR5342, available at https://trialsearch.who.int/Trial2.aspx?TrialID=NTR6687. The date of registration is July 31, 2015. The first enrollment is on January 1, 2016.

Comparing Vaginal and Endometrial Microbiota Using Culturomics: Proof of Concept

It is generally accepted that microorganisms can colonize a non-pathological endometrium. However, in a clinical setting, endometrial samples are always collected by passing through the vaginal-cervical route. As such, the vaginal and cervical microbiomes can easily cross-contaminate endometrial samples, resulting in a biased representation of the endometrial microbiome. This makes it difficult to demonstrate that the endometrial microbiome is not merely a reflection of contamination originating from sampling. Therefore, we investigated to what extent the endometrial microbiome corresponds to that of the vagina, applying culturomics on paired vaginal and endometrial samples. Culturomics could give novel insights into the microbiome of the female genital tract, as it overcomes sequencing-related bias. Ten subfertile women undergoing diagnostic hysteroscopy and endometrial biopsy were included. An additional vaginal swab was taken from each participant right before hysteroscopy. Both endometrial biopsies and vaginal swabs were analyzed using our previously described WASPLab-assisted culturomics protocol. In total, 101 bacterial and two fungal species were identified among these 10 patients. Fifty-six species were found in endometrial biopsies and 90 were found in vaginal swabs. On average, 28 % of species were found in both the endometrial biopsy and vaginal swab of a given patient. Of the 56 species found in the endometrial biopsies, 13 were not found in the vaginal swabs. Of the 90 species found in vaginal swabs, 47 were not found in the endometrium. Our culturomics-based approach sheds a different light on the current understanding of the endometrial microbiome. The data suggest the potential existence of a unique endometrial microbiome that is not merely a presentation of cross-contamination derived from sampling. However, we cannot exclude cross-contamination completely. In addition, we observe that the microbiome of the vagina is richer in species than that of the endometrium, which contradicts the current sequence-based literature.

The endometrial microbiota of women with or without a live birth within 12 months after a first failed IVF/ICSI cycle

The endometrial microbiota composition may be associated with implantation success. However, a 'core' composition has not yet been defined. This exploratory study analysed the endometrial microbiota by 16S rRNA sequencing (V1-V2 region) of 141 infertile women whose first IVF/ICSI cycle failed and compared the microbiota profiles of women with and without a live birth within 12 months of follow-up, and by infertility cause and type. Lactobacillus was the most abundant genus in the majority of samples. Women with a live birth compared to those without had significantly higher Lactobacillus crispatus relative abundance (RA) (p = 0.029), and a smaller proportion of them had ≤ 10% L. crispatus RA (42.1% and 70.4%, respectively; p = 0.015). A smaller proportion of women in the male factor infertility group had ≤ 10% L. crispatus RA compared to women in the unexplained and other infertility causes groups combined (p = 0.030). Women with primary infertility compared to secondary infertility had significantly higher L. crispatus RA (p = 0.004); lower proportions of them had ≤ 10% L. crispatus RA (p = 0.009) and > 10% Gardnerella vaginalis RA (p = 0.019). In conclusion, IVF/ICSI success may be associated with L. crispatus RA and secondary infertility with endometrial dysbiosis, more often than primary infertility. These hypotheses should be tested in rigorous well-powered longitudinal studies.

Individualized luteal phase support using additional oral dydrogesterone in artificially prepared frozen embryo transfer cycles: is it beneficial?

RESEARCH QUESTION

Does additional supplementation with oral dydrogesterone improve reproductive outcomes in patients with low serum progesterone concentrations on the day of frozen embryo transfer (FET) after artificial (HRT) endometrial preparation?

DESIGN

Retrospective, single-centre cohort study including 694 unique patients performing single blastocyst transfer in an HRT cycle. For luteal phase support, intravaginal micronized vaginal progesterone (MVP, 400 mg twice daily) was administered. Serum progesterone concentrations were assessed prior to FET and outco-mes were compared among patients with normal serum progesterone (≥8.8 ng/ml) continuing the routine protocol and patients with low serum progesterone (<8.8 ng/ml) who received additional oral dydrogesterone supplementation (10 mg three times daily) from the day after FET onwards. Primary outcome was live birth rate (LBR), with a multivariate regression model correcting for relevant confounders.

RESULTS

Normal serum progesterone concentrations were observed in 547/694 (78.8%) of patients who continued only MVP as planned, whereas low (<8.8 ng/ml) serum progesterone concentrations were detected in 147/694 (21.2%) patients who received additional oral dydrogesterone supplementation on top of MVP from the day after FET onwards. LBR was comparable between both groups: 37.8% for MVP-only versus 38.8% for MVP+OD (P = 0.84). The multivariate logistic regression model indicated that LBR was not significantly associated with the investigated approaches (adjusted odds ratio 1.01, 95% confidence interval 0.69-1.47, P = 0.97).

CONCLUSIONS

The current findings suggest that additional oral dydrogesterone supplementation in patients with low serum progesterone concentrations at the moment of transfer could have the potential to rescue reproductive outcomes in HRT-FET cycles. This field of research, however, remains hampered by the absence of randomized controlled trials.

Should we stop screening for chronic endometritis?

Chronic endometritis is a poorly understood infectious or inflammatory process, potentially disrupting the correct implantation of a human embryo (Puente et al., 2020). The exact prevalence is a subject of discussion and ranges across the available literature from 2% to almost 60%, with a higher suspicion of the condition being present in women with recurrent early pregnancy loss and recurrent implantation failure (Puente et al., 2020). The impact of chronic endometritis on reproductive outcomes following IVF remains questionable given the lack of proper data convincingly showing an improvement after diagnosis and treatment. This article aims to provide the reader with a critical appraisal of current diagnostic methods, treatments and patient populations to be tested for chronic endometritis.

Culturomics to Investigate the Endometrial Microbiome: Proof-of-Concept

The microbiome of the reproductive tract has been associated with (sub)fertility and it has been suggested that dysbiosis reduces success rates and pregnancy outcomes. The endometrial microbiome is of particular interest given the potential impact on the embryo implantation. To date, all endometrial microbiome studies have applied a metagenomics approach. A sequencing-based technique, however, has its limitations, more specifically in adequately exploring low-biomass settings, such as intra-uterine/endometrial samples. In this proof-of-concept study, we demonstrate the applicability of culturomics, a high-throughput culturing approach, to investigate the endometrial microbiome. Ten subfertile women undergoing diagnostic hysteroscopy and endometrial biopsy, as part of their routine work-up at Brussels IVF, were included after their informed consent. Biopsies were used to culture microbiota for up to 30 days in multiple aerobic and anaerobic conditions. Subsequent WASPLab®-assisted culturomics enabled a standardized methodology. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) or 16S rRNA sequencing was applied to identify all of bacterial and fungal isolates. Eighty-three bacterial and two fungal species were identified. The detected species were in concordance with previously published metagenomics-based endometrial microbiota analyses as 77 (91%) of them belonged to previously described genera. Nevertheless, highlighting the added value of culturomics to identify most isolates at the species level, 53 (62.4%) of the identified species were described in the endometrial microbiota for the first time. This study shows the applicability and added value of WASPLab®-assisted culturomics to investigate the low biomass endometrial microbiome at a species level.

Impact of cell loss after warming of human vitrified day 3 embryos on obstetric outcome in single frozen embryo transfers

PURPOSE

Does cell loss (CL) after vitrification and warming (V/W) of day 3 embryos have an impact on live birth rate (LBR) and neonatal outcomes?

METHOD

This retrospective analysis includes cleavage stage day 3 embryos vitrified/warmed between 2011 and 2018. Only single vitrified/warmed embryo transfers were included. Pre-implantation genetic screening, oocyte donation, and age banking were excluded from the analysis. The sample was divided into two groups: group A (intact embryo after warming) and group B (≤ 50% blastomere loss after warming).

RESULTS

On the total embryos (n = 2327), 1953 were fully intact (83.9%, group A) and 374 presented cell damage (16.1%, group B). In group B, 62% (232/374) of the embryos had lost only one cell. Age at cryopreservation, cause of infertility, insemination procedure, and semen origin were comparable between the two groups. The positive hCG rate (30% and 24.3%, respectively, for intact vs CL group, p = 0.028) and LBR (13.7% and 9.4%, respectively, for intact vs CL group, p = 0.023) per warming cycle were significantly higher for intact embryos. However, LBR per positive hCG was equivalent between intact and damaged embryos (45.6% vs 38.5%, respectively, p = 0.2). Newborn measurements (length, weight, and head circumference at birth) were comparable between the two groups. Multivariate logistic regression showed that the presence of CL is not predictive for LB when adjusting for patients' age.

CONCLUSIONS

LBR is significantly higher after transfer of an intact embryo compared to an embryo with CL after warming; however, neonatal outcomes are comparable between the two groups.

P-640 Impact of adding oral dydrogesterone (OD) in patients with low serum progesterone (P) levels in artificially prepared frozen embryo transfer cycles (FET-HRT)

Study question

In case of low serum P on the day of FET (PFET), does the addition of OD to micronized vaginal progesterone (MVP) normalise reproductive outcomes?

Summary answer

In case of low serum PFET, adding OD results in ongoing pregnancy rates (OPR) comparable to those of patients who had normal serum PFET.

What is known already

Low serum PFET is associated with increased rates of early pregnancy loss (EPL) and reduced live birth rates in FET HRT cycles. While adding subcutaneous P injections to vaginal progesterone has been shown to normalize clinical outcomes in case of low serum PFET, it is unknown whether adding OD has a similar effect.

Study design, size, duration

This is a retrospective, single-centre cohort study in a tertiary IVF-clinic. 694 unique patients who had a single blastocyst transfer in an HRT cycle were included. As soon as an endometrial thickness of ≥ 6.5mm was reached following estradiol valerate priming, MVP (400mg,twice daily) was started, followed by FET on the 6thday of MVP. All patients underwent serum P measurement just prior to FET. Serum PFET was analysed using a validated electrochemiluminescence immunoassay (Cobas 6000®,Roche).

Participants/materials, setting, methods

Clinical outcomes of patients with normal serum PFET(≥8,8ng/dl) following the routine MVPsupplementation were compared with those of patients with low serum PFET(&lt;8,8ng/dl) in whom OD(30mg TID) was added from FET onwards. Primary outcome was OPR, defined as a vital intra-uterine pregnancy at 8 weeks. EPL was defined as biochemical pregnancy loss or early miscarriage. A multivariate regression model was developed adjusting for age, BMI, endometrial thickness, embryo quality and estradiol level.

Main results and the role of chance

Mean age in the MVP-only versus the MVP+OD group was 34.6(±4.2) and 33.6(±4.3) years, respectively (p = 0.01). No other statistically significant differences were seen among both groups for BMI, endometrial thickness nor embryo quality. A normal serum PFET level was observed in 547/694 (78.8%) of patients, who continued MVP as planned, whereas a low serum PFET level was detected in 147/694 (21.2%) patients who received additional OD supplementation next to MVP from the day following FET onwards. The mean serum PFET level was 14.6 (±5.8) ng/ml in the MVP-only group and 7.0(±1.8) ng/ml in the MVP+OD group. The OPR was comparable between both groups: 40.8% for MVP only versus 40.0% for MVP+OD (p = 0.86). The biochemical pregnancy rates were 55.0% and 60.5% (p = 0.23) and the EPL rates were 14.4% and 21.1% (p = 0.05) in the MVP-only group vs. the MVP+OD group, respectively. Multivariate logistic regression analysis indicated that OPR was not associated with the investigated approaches (OR 0.92, SD 0.18, CI 0.63-1.35, p = 0.68). Only embryo quality was significantly associated with OPR (OR 3.03, SD 1.11, CI 1.48-6.21, p = 0.002).

Limitations, reasons for caution

The main limitation is the retrospective nature of this study with the risk of unmeasured confounder bias. While OPR is a less robust outcome parameter compared to LBR, LBR data will be presented once available.

Wider implications of the findings

Additional OD supplementation in patients with low P gives rise to comparable OPRs as observed in patients with normal P. Prospective studies are required to identify the individualized luteal phase support strategy that combines optimal LBR and low EPL rates.

Trial registration number

Not Applicable

P-510 Impact of ART on quality of life in predicted hyper-responders: conventional IVF versus in-vitro maturation of oocytes

Study question

Do in-vitro maturation (IVM) of oocytes and conventional IVF (cIVF) have different effects on quality of life (QoL) in women with polycystic ovaries (PCO)?

Summary answer

Women with PCO who have IVM treatment experienced a lower impact on QoL compared to their counterparts who underwent cIVF.

What is known already

While studies in predicted hyper-responders have shown that success rates of IVM are lower compared to cIVF, cIVF is associated with more hormonal side effects and complications including OHSS. According to a recent discrete choice experiment among hyper-responders in the Netherlands, not only success rates may play a role in these women’s preferences for fertility treatment, but also projected risks, burden, and costs. It is currently unknown whether the increased efficiency of cIVF in hyper-responders may come at the expense of impact on QoL and whether IVM may be associated with a lower impact on mental health parameters.

Study design, size, duration

This is a single-centre, observational prospective study including 149 women with polycystic ovaries on ultrasound scan who had their first cycle of IVM (n = 75) or cIVF (n = 74) in a tertiary referral hospital. Patients were included between May 2017 and March 2021.

Participants/materials, setting, methods

Patients &lt;37 years embarking on ART with their partner were asked to complete the Hospital Anxiety and Depression Scale (HADS) and the Fertility Quality of Life Questionnaire (FertiQoL) at three timepoints: intake at the fertility clinic (T1), at oocyte retrieval (T2) and after the first cycle outcome was known (T3). The primary objective was to determine the impact of ART on QoL. Statistical analysis included descriptive statistics and the use of general linear models.

Main results and the role of chance

In total, 124/149 (83.2%) patients completed questionnaires at two timepoints and 97/149 (65.1%) patients returned complete questionnaires. Mean age (28.92 ± 3.48y vs. 30.63 ± 3.23y, p = 0.003) was different in both groups. BMI (25.76 ± 5.81kg/m2 vs. 24.25 ± 4.83kg/m2, p = 0.089) and duration of infertility (27.12 ± 18.31 months vs. 31.00 ± 20.14 months, p = 0.270) were similar in IVM and cIVF patients, respectively. The distribution of PCOS phenotypes A, B, C and D, and PCOM was comparable in both groups (p = 0.142).

Univariable analysis showed that women undergoing cIVF had worse side effects scores at T2 than women who had IVM (5.09 ± 3.24 vs. 3.08 ± 2.43, p &lt; 0.001).

According to multivariable ANOVA, the impact of IVM on anxiety and depression scores was similar to that of cIVF. Patients undergoing IVM had better scores for the FertiQol Subscale for Treatment Tolerability (68.54 ± 16.75 vs. 59.09 ± 22.68, p = 0.011), suggesting that cIVF caused more mental symptoms and daily life disruption. The Relational Subscale at T3 indicated that IVM patients suffered less impairment of sexuality and communication. Finally, social interactions at T3 were more severely affected by cIVF than IVM based on the social FertiQoL subscale (74.57 ± 19.64 vs 66.96 ± 17.60, p = 0.039).

Limitations, reasons for caution

The type of ART was not assigned randomly, thus selection bias was highly likely because of the study design. The willingness to trade off chance of pregnancy for lower burden and risks may have influenced the choice of ART type and may have modulated susceptibility to impact on QoL.

Wider implications of the findings

Patients utilizing IVM may expect fewer side effects, more tolerability to treatment and less impact on their relationship and social life compared to those who opt for cIVF. Lower efficiency may be an acceptable trade-off for the benefits of IVM. These findings should be corroborated by an RCT.

Trial registration number

clinical trials.gov NCT03066349

O-254 Oral dydrogesterone (OD) versus micronized vaginal progesterone (MVP) for luteal phase support (LPS): impact on endometrium and genital tract microbiota

Study question

Is there a difference in the endometrial transcriptome and/or reproductive tract microbiota composition when OD versus MVP is used as LPS for fresh embryo transfer?

Summary answer

Endometrial transcriptome signatures and microbiota composition at the vaginal, cervical or intra-uterine site presented no significant differences following OD versus MVP.

What is known already

Adequate LPS is crucial to achieve a successful pregnancy following ovarian stimulation (OS) and fresh embryo transfer. OD has been proven to be non-inferior compared to MVP in two phase III clinical RCTs. Additionally, a combined individual participant data and aggregate data meta-analysis showed an odds ratio in favor of OD for live birth. Little information is available on the potential differences at the molecular level of the reproductive organs following the administration of either LPS strategies. Given the potential immunomodulating properties of OD, of main interest is the endometrial functionality and microbiota composition of the female genital tract.

Study design, size, duration

Thirty oocyte donors were planned to have two OS-cycles followed by one week of LPS (OD or MVP) in a randomized, cross-over, double-blind, double-dummy fashion. An endometrial biopsy, as well as vaginal/cervical/intra-uterine samples were collected. Endometrial RNA-sequencing was performed, raw reads were processed using STAR/htseq-count, differential gene expression was evaluated with EdgeR. Microbiota profiles were obtained by 16S-rRNA-sequencing using the DADA2-pipeline with RDP-classifier. Comparative analysis of genera relative abundances was performed in R.

Participants/materials, setting, methods

All oocyte donors were &lt;35 years old, had regular menstrual cycles, no intra-uterine contraceptive device, AMH within normal range and BMI≤ 29 kg/m2. OS was performed in a GnRH antagonist protocol followed by dual triggering (1000U hCG + 0.2mg triptorelin) as soon as ≥ 3 follicles of 20mm were present. Following oocyte retrieval, subjects initiated LPS consisting of MVP 200 mg (Utrogestan®) or OD 10 mg (Duphaston®), both three times daily.

Main results and the role of chance

Subject and stimulation characteristics were comparable between the groups. For endometrial RNA-sequencing, 21 pairs (n = 42 biopsies) were available with the same oocyte donor having a biopsy after OD as well as after MVP (the remaining 9 subjects were excluded due to late follicular progesterone elevation/drop-out after one cycle). After correction for multiple hypothesis testing, no differentially expressed genes could be withheld and the principal component analysis plot showed one mixed OD/MVP cluster (PCA1 25% variance, PCA2 16% variance). The average Euclidean distance between samples of the OD group was significantly lower than for the MVP group (respectively 12.1 vs 18.8, comparison of the two-group wise Euclidean distributions results in p = 6.98e-14 using the Mann-Whitney test).

Microbiota profiling was performed before and after OD/MVP (4 collections per subject). Samples with insufficient high-quality reads were excluded, resulting in 42 intra-uterine samplings, 82 cervical and 84 vaginal swabs used for analysis. No difference was seen at any site of the female reproductive tract following OD versus MVP in microbiota diversity, richness, genera abundances (delta contrasts [Mann–Whitney U test], padj &gt; 0.1), nor community composition (dbRDA genus-level Euclidean distances in vagina [R2= 0.22%, padj=0.26], cervix [R2= 0.36%, padj=0.20], uterus [R2= -0.06%, padj=0.45]).

Limitations, reasons for caution

Sample size was limited. Whole tissue endometrial transcriptomics was performed on individual biopsies without accounting for the potential bias of different tissue compartment compositions among biopsies. As it was a double blind, double dummy study design, the impact of not administering medication via the vaginal route could not be evaluated.

Wider implications of the findings

This is the first molecular study comparing OD/MVP. Results show that there is no difference between OD/MVP’s ability to give rise to the receptive state, which corresponds with the clinical trial data. As the inter-sample distance of RNA-profiles was smaller following OD, interindividual variations could be lower for this approach.

Trial registration number

EUDRACT 2018-000105-23

P-409 The endometrial transcriptome of infertile women with and without recurrent implantation failure

Study question

Does the endometrial transcriptome profile differ between infertile women with or without a recurrent implantation failure (RIF)?

Summary answer

Although two different clusters emerged from the endometrial transcriptome data, these were not associated with clinical phenotype (RIF vs non-RIF).

What is known already

Despite the transfer of morphologically ‘good-quality’ embryos in IVF/ICSI, implantation failure often occurs, which may be explained by impaired endometrial receptivity. In order to guide prognosis and use effective therapeutic interventions, identifying a gene expression profile predictive of endometrial receptivity as well as implantation failure, would be of great value. Additionally, transcriptome analysis may also shed light on alterations in biological processes responsible for the implantation failure. Thousands of potential biomarkers for endometrial receptivity have already been identified by transcriptomic approach, however due to differences in study methodology, there is little overlap of markers between studies.

Study design, size, duration

Endometrial tissue was obtained from a cohort of 141 infertile women undergoing endometrial scratching within a randomised controlled trial (RCT) (SCRaTCH trial, NL5193/NTR5342). Briefly, women aged 18-44 years with failed implantation after one full IVF/ICSI cycle and planning a subsequent IVF/ICSI cycle, were eligible. Participants were followed-up until 12 months after randomisation, with the primary outcome being live birth, defined as the delivery of at least one live foetus after 24 weeks of gestation.

Participants/materials, setting, methods

Endometrial tissue was obtained with an endometrial biopsy catheter in the midluteal phase of a natural cycle preceding subsequent IVF/ICSI. Biopsies were snap-frozen and stored at -80 °C until use. After thawing, total RNA isolation, library preparation and paired-end RNA-sequencing were performed. Raw data was preprocessed and mapped to GRCh38. Reads (counts per million) were normalised using library size. Differential gene expression (DGE) analysis was conducted using the EdgeR package with significance threshold FDR &lt;0.05.

Main results and the role of chance

Out of 141 endometrium samples, 107 were included in the RNA-sequencing based on RNA quality. For DGE analysis, data of two groups were compared: the ‘fertile’ group, women with a live birth after ≤3 good quality embryo(s) transfers (n = 23), and the RIF group, women with no live birth after ≥3 good quality embryo(s) transfers (n = 23). Two clusters were visible in the principle component analysis (PCA) plot showing transcriptome data of the fertile and RIF samples (cluster 1, n = 29; cluster 2, n = 10), which was not explained by clinical phenotype, as both clusters contained samples of both the fertile and RIF group. DGE analysis between the fertile and RIF group resulted in respectively 3 significantly upregulated and 0 significantly downregulated genes, whereas DGE analysis between the two clusters resulted in 2,235 significantly upregulated and 2,162 significantly downregulated genes. Enrichment analysis of differentially expressed genes between both clusters demonstrated upregulation of enriched terms mainly annotated to cell migration and downregulation of enriched terms mainly annotated to lipid and mitochondrial metabolism.

Limitations, reasons for caution

A strength of the study is the large number of samples included. Bulk RNA-sequencing was conducted and there was a variation in LH-based timing of the biopsies (5-8 days after LH surge) for which adjustments of the transcriptome data for tissue cellular composition and menstrual cycle were performed.

Wider implications of the findings

Future studies investigating underlying biological mechanisms in the endometrium in (in)fertility by a (multi-)omics analysis approach with standardised methodology are required to obtain consistencies in relevant biomarkers/pathways, and in due course create possibilities to improve and personalise care for infertile couples.

Trial registration number

NL5193/NTR5342

P-669 The impact of luteal phase support on pregnancy outcomes in relation to serum progesterone levels on the day of frozen embryo transfer in natural cycles

Study question

Is luteal phase support (LPS) beneficial in low and normal serum progesterone (P) levels the day of frozen embryo transfer (FET) in natural cycles (NC)?

Summary answer

LPS in case of low serum P on the day of NC-FET results in similar pregnancy rates as compared to patients with normal P levels.

What is known already

The use of FET cycles has increased exponentially in recent years. Endometrial preparation in FET cycles can be achieved either in a natural cycle, a stimulated cycle or in an artificial cycle (AC). There is increasing evidence that proper serum P levels around the time of FET are important in AC and NC. Recent studies in AC have shown that enhanced progesterone supplementation in case of low serum P levels could reduce early pregnancy loss rates and normalize live birth rates. Whether this rescue strategy could also be beneficial in NC-FET has not been investigated in detail.

Study design, size, duration

A retrospective study was conducted at a tertiary university-based referral hospital encompassing 459 unique patients who had a NC-FET with or without hCG trigger from November 2020 onwards. Only patients who had an in-house validated serum P measurement (Cobas 6000®,Roche) on the day of FET were included. Blastocyst transfer was performed 6 days after a spontaneous luteinizing hormone (LH) peak or 7 days after hCG administration. Ongoing pregnancy rate (OPR) was the primary outcome.

Participants/materials, setting, methods

Outcomes were compared in patients with low serum P (&lt;10ng/dl) levels, who received LPS from the day of FET onwards (group 1) and patients with normal serum P (≥10ng/dl) levels (group 2). Group 2 was subdivided into patients who did not received LPS (group 2a) and patients who did (group 2b), as by practitioner’s choice. Multivariable regression analysis was performed adjusting for age, BMI, endometrial thickness, rank of FET, embryo quality and indication for treatment.

Main results and the role of chance

Mean ages were 31.8 years (group 1) and 33.3 years (group 2, p = 0.004). BMI was significantly lower in group 2 (23.7 kg/m2) compared to group 1 (26.7 kg/m2, p &lt; 0.001). Indication for treatment, menstrual cycle length, anti-Mullerian hormone (AMH) levels and parity were comparable between both groups. An hCG ovulation trigger was administered in 26.0% of the cycles in group 1 and 20.4% in group 2 (p = 0.28). Endometrial thickness was equal in both groups (8.3mm, p = 0.84). In group 1, 40.3% of the patients had a transfer of a top quality embryo as compared to 46.3% in group 2 (p = 0.33).

Positive hCG rate (54.6%, 64.0% and 65.0% for group 1, 2a and 2b respectively, p = 0.26) and miscarriage rate per positive hCG (2.4%, 9.2% and 6.7% for group 1,2a and 2b respectively, p = 0.37) were comparable between groups.

OPR per started cycle was similar between groups (46.8%, 55.4% and 55.6% for group 1, 2a and 2b respectively, p = 0.37). Multivariable logistic regression analysis showed no relationship between OPR and the three different groups (p = 0.13). A significant association was observed between OPR and patient age at embryo cryopreservation.

Limitations, reasons for caution

Although only patients were included who had serum P levels on the day of FET measured by a standardized in-house assay, the results of the study are limited by the retrospective nature and its associated bias. Confirmation of the results should be obtained in prospective studies.

Wider implications of the findings

Luteal phase deficiency was observed in only 16.8% of patients in our study population. Administration of LPS in patients with low serum P levels on the day of FET could rescue pregnancy outcomes. However, starting LPS when serum P levels are normal appears to have no added value.

Trial registration number

not applicable

P-401 The impact of the recipients’ age in vitrified/warmed oocyte donation (OD) cycles

Study question

Does female age affect reproductive outcomes in a vitrified/warmed OD program with fresh embryo transfer?

Summary answer

Oocyte donation performed below the age of 40 was associated with less favorable reproductive outcomes.

What is known already

It is well established that oocyte and embryo aneuploidy are mainly responsible for the age-related decline in female fertility. Previous studies evaluating the effect of maternal age on implantation potential in OD cycles generated controversial results. It remains unclear whether female age affects reproductive outcome independent of embryo quality.

Study design, size, duration

This is a retrospective, single tertiary center, cohort study analyzing a vitrified/warmed OD program over a ten-years period (February 2010-February 2020). More specifically, data from 491 unique oocyte recipients were included who performed a fresh embryo transfer after sharing (with at least two recipients) sibling oocytes from the same donor stimulation cycle. For all treatments ICSI was performed without preimplantation genetic testing.

Participants/materials, setting, methods

The association between recipient’s age and reproductive outcomes was investigated according to three age categories (&lt;35/35-40/&gt;40 years old). The primary outcome was live birth rate (LBR), while the secondary outcome was biochemical pregnancy rate (BPR). A multivariate regression model was developed adjusting for the following covariates (entered simultaneously): recipient’s BMI, recipient’s endometrial thickness, age of the oocyte donor, number of mature oocytes used for ICSI, embryo transfer stage and number of embryos transferred.

Main results and the role of chance

Mean age of donors was 28.6 years old(±4.1). Mean starting dose was 192.6 IU(±139.9) and duration of stimulation 11.0 days (±1.7). Mean number of collected cumulus oocyte complexes was 25.6(±9.6) and sibling oocytes were assigned to 2, 3 or more recipients in, respectively, 83.1%, 12.4% and 4.5% of cases.

Mean age of recipients was 38.6 years old(±5.1), BMI 24.3 kg/m²(±4.1) and endometrial thickness 8.9mm(±2.1). ICSI was performed on a mean number of 6.5 (±2.0) warmed, intact, mature oocytes with a fertilization rate of 68.2% (±22.5). Cleavage-stage embryos were transferred in 91.0% of the recipients, with a double embryo transfer in 42.6%. 81.3% of embryos were scored as top-quality and a mean of 1.4 (±1.4) surplus embryos were available for additional vitrification.

Overall BPR was 44.2%, clinical pregnancy rate 39.3% and LBR 31.0%. Categorizing according to recipient’s age showed a LBR of 24.3%,26.7% and 37.0% for, respectively, the group &lt;35, 35-40 and &gt;40 years old (p = 0.02). The multivariate GEE regression model confirmed the crude data showing that the age was a significant positive predictor of LBR [coefficient (-), 0.01,0.11, for group&lt;35,35-40 and &gt;40 years old, p = 0.05] and BPR [coefficient (-),0.008,0.15, for group &lt;35,35-40 and &gt;40 years old, p = 0.006].

Limitations, reasons for caution

Sibling donor oocytes were used, but the retrospective nature of the study remains a reason for caution. Also, the fact that the majority of embryos were transferred at the cleavage stage is a limitation.

Wider implications of the findings

The observation that recipients below the age of 40 have lower reproductive success rates following oocyte donation deserves further attention. The need for oocyte donation at younger age might be associated with a less performant uterine/endometrial function due to underlying conditions of genetic and/or endocrine nature.

Trial registration number

B1432020000146

O-069 Does dual stimulation with continuous FSH administration increase the total number of metaphase II oocytes in poor responders?

Study question

Is there an increase in the total number of metaphase II (MII) oocytes between a conventional ovarian stimulation and a dual uninterrupted stimulation?

Summary answer

Dual stimulation with continuous follicle stimulating hormone (FSH) administration is not superior to conventional stimulation in terms of number of MII oocytes.

What is known already

In the last decade, the concept of multiple follicular waves during one menstrual cycle has gained a lot of interest. Translated into clinical practice, combining two stimulations in the same ovarian cycle has appeared beneficial with regard to the number of retrieved oocytes, without affecting the embryo quality or ploidy status. Usually, this so-called dual stimulation approach is characterized by a discontinuation of FSH administration for approximately 5 days between two consecutive stimulations. The role of dual uninterrupted ovarian stimulation has not yet been studied.

Study design, size, duration

This was an open-label randomized controlled trial (RCT) with superiority design, performed in a single tertiary center. Power analysis indicated a required sample of 46 patients to detect superiority (defined as two surplus MII oocytes) of the dual stimulation group. Between October 2020 and September 2021, 70 patients were screened, 48 were randomized and 46 completed the study.

Participants/materials, setting, methods

Women aged 25-40 with a serum anti-Müllerian hormone (AMH) level of ≤ 1.5 ng/mL, antral follicle count (AFC) of ≤ 6, or ≤ 5 oocytes after a previous stimulation, were eligible for inclusion. Randomization occurred only in case of ≤ 9 follicles of ≥ 11mm on the trigger day. In the control group, patients underwent one round of ovarian stimulation and oocyte retrieval only, while the study group had two uninterrupted rounds of ovarian stimulation and two retrievals.

Main results and the role of chance

Baseline characteristics were similar between both groups. The cumulative number of COC and MII oocytes after completion of the second oocyte retrieval was similar in the control and study group [5.3 ± 2.7 versus 5.3 ± 3.1 [difference 95%CI (-1.7 to 1.7), p = 0.92] and 4.1 ± 2.5 versus 4.3 ± 2.7 [difference 95%CI (-1.7 to 1.3), p = 0.82]. Likewise, a comparable number of good quality embryos at day 3 was available (3.0 ± 2.0 versus 2.7 ± 2., p = 0.63). In the study group, the cancellation rate due to insufficient response to the second round of stimulation was 39.1%.

When focusing on the first stimulation in both groups, there were no significant differences regarding basal FSH, FSH consumption and the number of preovulatory follicles. After the first oocyte retrieval, the mean number of COC and MII oocytes was significantly higher in the control group (who had human chorionic gonadotropin (hCG) triggering), compared to the study group (who had Gonadotropin Releasing Hormone (GnRH) agonist triggering) (5.3 ± 2.7 versus 3.3 ± 2.2, p = 0.004 and 4.2 ± 2.4 versus 2.9 ± 2.2, p = 0.05). Likewise, the number of good quality embryos on day 3 was significantly higher (3.0 ± 2.0 versus 1.9 ± 1.7, p = 0.04).

Limitations, reasons for caution

This study was powered to demonstrate superiority for number of MII oocytes. Investigating the impact of dual stimulation on pregnancy rates would have required a larger sample size.

Wider implications of the findings

The observed suboptimal oocyte yield after agonist triggering in poor responders is a reason for concern and further scrutiny, given that previous RCTs have shown similar outcomes in normal and high responders after hCG and GnRH agonist trigger.

Trial registration number

NCT03846544

Cumulative live birth rate after ovarian stimulation with freeze-all in women with polycystic ovaries: does the polycystic ovary syndrome phenotype have an impact?

RESEARCH QUESTION

Do cumulative live birth rates (CLBR) differ between polycystic ovary syndrome (PCOS) phenotypes when a freeze-all strategy is used to prevent OHSS after ovarian stimulation?

DESIGN

A single-centre, retrospective cohort study of 422 women with PCOS or polycystic ovarian morphology (PCOM), in whom a freeze-all strategy was applied after GnRH agonist triggering because of hyper-response in their first or second IVF/ICSI. Primary outcome was CLBR; multivariate logistic regression analysis was used.

RESULTS

Phenotype A (hyperandrogenism + ovulation disorder + PCOM [HOP]) (n = 91/422 [21.6%]); phenotype C (hyperandrogenism + PCOM [HP]) (33/422 [7.8%]; phenotype D (ovulation disorder + PCOM [OP]) (n = 161/422 [38.2%]); and PCOM (n = 137/422 [32.5%]. Unadjusted CLBR was similar among the groups (69.2%, 69.7%, 79.5% and 67.9%, respectively; P = 0.11). According to multivariate logistic regression analysis, the phenotype did not affect CLBR (OR 0.72, CI 0.24 to 2.14 [phenotype C]; OR 1.55, CI 0.71 to 3.36 [phenotype D]; OR 0.84, CI 0.39 to 1.83 [PCOM]; P = 0.2, with phenotype A as reference).

CONCLUSIONS

In women with PCOS, hyper-response after ovarian stimulation confers CLBR of around 70%, irrespective of phenotype, when a freeze-all strategy is used. This contrasts with unfavourable clinical outcomes in women with hyperandrogenism and women with PCOS who underwent mild ovarian stimulation targeting normal ovarian response and fresh embryo transfer. The results should be interpreted with caution because the study is retrospective and cannot be generalized to all cycles as they pertain to those in which hyper-response is observed.

O-127 The endometrial tissue microbiota of women who did or did not achieve a live birth within 12 months after a first failed IVF/ICSI cycle

Study question

After one failed IVF/ICSI cycle, does the endometrial microbiota composition differ between women who will or will not reach a live birth within 12 months?

Summary answer

The endometrial microbiota composition did not significantly differ in women with one failed IVF/ICSI cycle with or without live birth, but statistical power was low.

What is known already

Evidence for the presence of an indigenous endometrial microbiome is mounting, and its composition may be associated with implantation success. However, a ‘core’ endometrial microbiome has not yet been defined, and its role in embryo implantation is still poorly understood. Further investigation of this topic may allow improvement and personalisation of clinical care for infertile couples. Endometrial microbiome analysis in infertile women has not yet been performed using transcervically obtained endometrial tissue. Using endometrial tissue instead of swabs or fluid may increase the bacterial DNA yield and therefore the precision of microbiome analyses.

Study design, size, duration

Endometrial tissue was obtained from a cohort of 141 infertile women undergoing endometrial scratching within a randomised controlled trial (RCT) (SCRaTCH trial, NL5193/NTR5342). Briefly, women aged 18-44 years with failed implantation after one full IVF/ICSI cycle and planning a subsequent IVF/ICSI cycle, were eligible. Participants were followed-up until 12 months after randomisation, with the primary outcome being live birth, defined as the delivery of at least one live foetus after 24 weeks of gestation.

Participants/materials, setting, methods

Endometrial tissue was obtained with an endometrial biopsy catheter in the midluteal phase of a natural cycle preceding subsequent IVF/ICSI, snap-frozen and stored at -80 °C until use. Total DNA was isolated from these biopsies, followed by 16S rRNA sequencing (V3-V4 region) to determine the endometrial microbiota composition. Positive (mock communities) and negative controls (DNA extraction and PCRs) were included. QIIME2 and DADA2 were used for the data analysis, followed by statistical analysis in R studio.

Main results and the role of chance

During the 12-month follow-up, 61/141 women (43.3%) reached a live birth. While endometrial microbiota profiles of all 141 women were analysed, only samples with ≥100 reads were included in the analysis, resulting in a total of 46 samples (32.6%) that were included in the analysis, which consisted of samples from 25 women who did not have and 21 women who did have a live birth within 12 months. The median number of reads per sample was not significantly different between the two groups (respectively 2,317 (IQR 651-19,031) and 1,335 (IQR 296-3,180), p = 0.29 by Mann-Whitney test). The endometrial microbiota detected, were bacterial genera frequently reported within the vaginal microbiota (e.g. Lactobacillus, Atopobium and Gardnerella). A clear dominance of Lactobacillus (relative abundance 55-100%, n = 22) or an unclassified bacterium genus (relative abundance 52-76%, n = 18) was observed in the majority of the samples; however, this dominance was not associated with the outcome of live birth. In addition, the samples dominated by Lactobacillus genera were mostly dominated by one species of Lactobacillus each (L. crispatus, L. iners, L. gasseri or L. jensenii).

Limitations, reasons for caution

The low biomass and the low ratio of bacterial versus human DNA in endometrial tissue were limiting factors in endometrial microbiota analysis. Furthermore, tissue was obtained transcervically, and contamination with vaginal/cervical microbiota could therefore have occurred. In the SCRaTCH trial no vaginal swabs were taken to serve as internal controls.

Wider implications of the findings

Future endometrial microbiota studies should consider the use of samples with a lower proportion of human DNA to maximize bacterial DNA yield. Furthermore, for endometrial microbiota research, sampling devices avoiding cervicovaginal contamination are desirable and may be developed in the future.

Trial registration number

SCRaTCH trial, NL5193/NTR5342

P–684 Impact of GnRH antagonist pretreatment on oocyte yield after ovarian stimulation: a retrospective analysis

Study question

Does a 3-day pretreatment course with a GnRH antagonist in the early follicular phase increase the number of oocytes in a GnRH antagonist stimulation protocol?

Summary answer

The administration of 3 days of GnRH antagonist before starting ovarian stimulation in a GnRH antagonist protocol increases the number of COCs (Cumulus-Oocyte-Complexes).

What is known already

The GnRH antagonist protocol is characterized by higher gonadotropin and E2 serum levels at the start of ovarian stimulation (OS), compared with a long pituitary down regulation protocol. The unsuppressed FSH level at the start of a GnRH antagonist cycle allows the initial growth of follicles before addition of exogenous FSH, which may result in asynchrony of the follicular cohort. Menstrual administration of a GnRH antagonist can inhibit follicle growth and improve homogeneity of recruitable follicles. Previous studies showed a trend toward higher numbers of COCs and improved maturation and fertilization rates of retrieved oocytes.

Study design, size, duration

Retrospective single center crossover study, including consecutive women enrolled in an IVF program in a university hospital from January 2011 to December 2020. All women underwent one standard GnRH antagonist stimulation cycle (“standard cycle”) and one GnRH antagonist stimulation cycle preceded by early administration of GnRH antagonist for 3 days (“pretreatment cycle”). Women with basal progesterone levels &gt;1.5ng/ml, and women undergoing oocyte freezing, oocyte donation or PGT were excluded. In total, 427 patients were included.

Participants/materials, setting, methods

Women were included when the pretreatment cycle occurred within a time interval of &lt; 12 months following the start of stimulation in the standard cycle. The primary outcome was the total number of COCs.

Main results and the role of chance

The average female age was 35.1 ± 4.7 years. Indications for fertility treatment included unexplained infertility (34.3%), male-factor infertility (33.3%), age (16.9%), PCOS (8.2%) and endometriosis (2.6%). All cycles were divided into two groups: group 1 (standard, 427 cycles) and group 2 (pretreatment, 427 cycles). The mean duration of stimulation was similar in both groups (10.3 vs 10.3 days, p = 0.2). The starting dose of gonadotropin (196.8 vs 234.9IU, p &lt; 0.001) and total amount of gonadotropin used (2000.7 vs 2415.2IU, p &lt; 0.001) were higher in group 2. The total number of obtained COCs (6.2 vs 8.8 p &lt; 0.001) and the number of mature oocytes (4.2 vs 6.4 p &lt; 0.001) were significantly higher in group 2. The Generalized estimating equation (GEE) multivariate regression analysis showed that the pretreatment strategy had a significant positive effect on the number of COCs (coefficient 2.8, p value &lt;0.001 after adjusting for the confounders age, indication of infertility, stimulation dose, type and total amount of gonatropins used).

Limitations, reasons for caution

Despite the large dataset, the presence of biases related to the retrospective study design cannot be excluded. Besides, the impact of GnRH pretreatment on pregnancy rate cannot be assessed because of the crossover design.

Wider implications of the findings: A 3-day course of GnRH antagonist pretreatment increases the number of COCs obtained after OS. Furthermore, since the initiation of OS in a GnRH antagonist protocol relies on the occurrence of spontaneous menses, addition of three days of GnRH antagonist pretreatment may enhance scheduling flexibility without reducing efficacy.

Trial registration number

Not applicable

P–318 Short (seven days) versus conventional (fourteen days) estrogen priming in an artificial frozen embryo transfer cycle: a randomised controlled trial

Study question

What is the impact of seven days versus fourteen days’ estrogen (E2) priming on the clinical outcome of frozen-embryo-transfer in artificially prepared endometrium (FET-HRT) cycles?

Summary answer

No significant difference in clinical/ongoing pregnancy rate was observed when comparing 7 versus 14 days of estrogen priming before starting progesterone (P) supplementation.

What is known already

One (effective) method for endometrial preparation prior to frozen embryo transfer is hormone replacement therapy (HRT), a sequential regimen with E2 and P, which aims to mimic the endocrine exposure of the endometrium in a physiological cycle. The average duration of E2 supplementation is generally 12–14 days, however, this protocol has been arbitrarily chosen whereas, the optimal duration of E2 implementation remains unknown.

Study design, size, duration

This is a single-center, randomized, controlled, open-label pilot study. All FET-HRT cycles were performed in a tertiary centre between October 2018 and December 2020. Overall, 150 patients were randomized of whom 132 were included in the analysis after screening failure and drop-out.

Participants/materials, setting, methods

The included patients were randomized into one of 2 groups; group A (7 days of E2 prior to P supplementation) and group B (14 days of E2 prior to P supplementation). Both groups received blastocyst stage embryos for transfer on the 6th day of vaginal P administration. Pregnancy was assessed by an hCG blood test 12 days after FET and clinical pregnancy was confirmed by transvaginal ultrasound at 7 weeks of gestation.

Main results and the role of chance

Following the exclusion of drop-outs and screening failures, 132 patients were finally included both in group A (69 patients) or group B (63 patients). Demographic characteristics for both groups were comparable. The positive pregnancy rate was 46.4% and 53.9%, (p 0.462) for group A and group B, respectively. With regard to the clinical pregnancy rate at 7 weeks, no statistically significant difference was observed (36.2% vs 36.5% for group A and group B, respectively, p = 0.499). The secondary outcomes of the study (biochemical pregnancy, miscarriage and live birth rate) were also comparable between the two arms for both PP and ITT analysis. Multivariable logistic regression showed that the HRT scheme is not associated with pregnancy rate, however, the P value on the day of ET is significantly associated with the pregnancy outcome.

Limitations, reasons for caution

This study was designed as a proof of principle trial with a limited study population and therefore underpowered to determine the superiority of one intervention over another. Instead, the purpose of the present study was to explore trends in outcome differences and to allow us to safely design larger RCTs.

Wider implications of the findings: The results of this study give the confidence to perform larger-scale RCTs to confirm whether a FET-HRT can be performed safely in a shorter time frame, thus, reducing the TTP, while maintaining comparable pregnancy and live birth rates.

Trial registration number

NCT03930706

P–707 Does the dose or type of gonadotropin affect the reproductive outcomes of poor responders undergoing modified natural cycle IVF (MNC-IVF)?

Study question

Does the dose or type of gonadotropin affect the reproductive outcomes of poor responders undergoing MNC-IVF?

Summary answer

Neither the type nor the dose of gonadotropins affects the reproductive outcomes of poor responders undergoing MNC-IVF.

What is known already

Poor ovarian response (POR) to ovarian stimulation remains a major therapeutic challenge in routine IVF practice, because of the association with low live birth rates and high cancellation rates. Although high doses of gonadotropins are traditionally used to stimulate the ovaries in women with predicted POR, MNC-IVF has been proposed as a mild-approach alternative in this population. Typically, the MNC protocol includes GnRH-antagonists to avoid premature ovulation and gonadotropin add-back stimulation at the late follicular phase. However, evidence is sparse, and there is no consensus regarding a specific dose or type of gonadotropins in this mild stimulation protocol.

Study design, size, duration

This is a retrospective cohort study including patients attending a tertiary referral University Hospital from 1st January 2017 until 1st March 2020.

Participants/materials, setting, methods

All women who underwent MNC-IVF in our center were included. Gonadotropins [recombinant FSH (rFSH), urinary FSH (uFSH) or highly purified human menopausal gonadotrophin (hp-hMG)] were started when a follicle with a mean diameter of 12–14 mm was observed on ultrasound scan, followed by GnRH antagonists (0.25mg/day) from the next day onwards. Mature oocytes were inseminated using ICSI.

Main results and the role of chance

In total, 484 patients undergoing 1398 cycles were included. Mean (SD) age and serum AMH were 38.2 (3.7) years and 0.46 (0.78) ng/ml, respectively. The daily dose of gonadotropins was either &lt;75 IU/d [11/1398 (0.8%)] or 75 to &lt; 100 IU/d [1303/1398 (93.2%)] or ≥ 100 IU/d [84/1398 (6%)]. Patients were stimulated with: rFSH [251/1398 (18%)], uFSH [45/1398 (3.2%)] or hp-hMG [1102/1398 (78.8%)]. Biochemical and clinical pregnancy rates were 142/1398 (10.1%) and 119/1398 (8.5%). Live birth was achieved in 80/1398 (5.7%) of cycles. Live birth rates (LBR) were similar between the different type and doses of gonadotropins (p-value 0.3 and 0.51, respectively). The GEE multivariate regression analysis adjusting for relevant confounders (age, BMI, number of MII oocytes) showed that the type of treatment strategy (rFSH/uFSH/hp-hMG) and the dose of gonadotropins were not significantly associated with LBR (coefficient 0.01 and –0.02, p value 0.09 and 0.3, respectively).

Limitations, reasons for caution

The main limitation is the retrospective design of our study, with an inherent risk of bias.

Wider implications of the findings: This is the first and largest study evaluating MNC-IVF protocol modalities. Our data demonstrate that any type of gonadotropin can be used and there is no benefit from daily doses beyond 75IU.

Trial registration number

N/A

P–464 What is the optimal ovarian stimulation (OS) protocol for women who undergo planned oocyte cryopreservation (POC)?

Study question

When repeated cycles of OS for planned oocyte cryopreservation using a standard GnRH antagonist protocol are required, can OS protocol modifications improve oocyte yield?

Summary answer

Compared to repeating a standard GnRH antagonist protocol, switching to a long GnRH agonist protocol for POC results in a higher number of cryopreserved oocytes.

What is known already

The total number of cryopreserved oocytes is a key parameter of POC programs because of its association with livebirth. A substantial proportion of women embarking on POC will undergo repeated cycles of OS to reach their desired target number of vitrified oocytes. According to recent guidelines, the GnRH antagonist protocol with GnRH agonist triggering is considered the first choice protocol for POC, because of its safety profile and convenience. However, in women with normal ovarian reserve, the long GnRH agonist protocol results in a higher number of oocytes retrieved. Evidence regarding the optimal protocol for POC is limited.

Study design, size, duration

This is a single-centre, retrospective cohort study including 283 women who had a first cycle for POC using a standard GnRH antagonist protocol and who requested a second OS cycle to increase their total number of vitrified oocytes for later use. The choice of protocol for the second cycle was left at the discretion of the reproductive medicine specialist. All OS cycles took place between January 2009 and December 2019 in a tertiary referral hospital.

Participants/materials, setting, methods

After ovarian reserve testing, the first cycle OS was performed using rFSH or HPhMG in a GnRH antagonist protocol. For the second cycle, a GnRH antagonist protocol with or without antagonist pretreatment, or a long GnRH agonist protocol was prescribed. The primary outcome was the number of mature oocytes (MII) vitrified per cycle. Cycle characteristics were compared. Data were assessed by generalized estimating equation (GEE) regression analysis adjusting for covariates.

Main results and the role of chance

In total, 226 (79.9%) women had a GnRH antagonist protocol and 57 (20.1%) had a long GnRH agonist protocol in their second OS cycle for POC. Overall, mean age was 36.6±2.4 years. The median (CI) number of mature oocytes vitrified after the second OS cycle was significantly higher than that after the first cycle [8 (5–11) vs. 7 (4–10), p &lt; 0.001]. According to GEE multivariate regression, adjusting for relevant confounders, switching from a GnRH antagonist protocol in the first cycle to a long GnRH agonist protocol in the second cycle was the only significant predictor of the number of vitrified oocytes after the subsequent cycle (coefficient 1.59, CI 0.29–2.89, p-value = 0.017). Age, AFC, initial dose and type of gonadotropins did not predict the number of vitrified oocytes. None of the women developed moderate or severe OHSS.

Similarly, of 174 women who underwent their first OS cycle with a standard GnRH antagonist protocol, 133 women (76.4%) had the same protocol for their second cycle and 41 women (23.6%) an additional three-day course of GnRH antagonist pretreatment. According to GEE multivariate regression, this protocol modification did not result in more mature oocytes available for vitrification (coefficient –0.25, CI –1.86–1.36, p-value = 0.76).

Limitations, reasons for caution

These data should be interpreted with caution because of the retrospective design and limited sample. Although more oocytes were obtained with a long GnRH agonist protocol we have no data on livebirth in women returning to use their oocytes to support the choice for a specific OS protocol for POC.

Wider implications of the findings: Although oocyte yield in the context of POC is an important parameter that may be modulated by the choice of OS protocol, the ultimate outcome measure of a successful POC program is livebirth after oocyte vitrification. Future research of oocyte parameters reflecting oocyte quality is paramount.

Trial registration number

Not applicable

O-161 Cumulative live birth rate after a freeze-all approach in women with polycystic ovaries: does the PCOS phenotype have an impact?

Study question

Do cumulative live birth rates (CLBR) differ between PCOS phenotypes when a freeze-all strategy is used to prevent OHSS after ovarian stimulation (OS)?

Summary answer

When conventional-dose OS resulted in high response, a CLBR of ∼ 70% was observed after “freeze-all” in women with PCOS, irrespective of their phenotype.

What is known already

Previous observational studies have shown that CLBR in women with PCOS who undergo assisted reproductive technologies (ART) may depend on their phenotype. When OS was performed with caution to avoid ovarian hyperresponse, CLBR was lower in women with a hyperandrogenic PCOS phenotype. However, when women with PCOS do exhibit hyperresponse and a freeze-all strategy is used, the impact of the PCOS phenotype on the clinical outcome of the ART cycle is unclear.

Study design, size, duration

This is a single-centre, retrospective cohort study including 422 women with polycystic ovary syndrome (PCOS) as defined by Rotterdam criteria or PCO-like ovarian morphology-only (PCOM) in whom a freeze-all strategy was applied after GnRH agonist triggering in the context of hyperresponse defined as ³19 follicles of ³11mm in their first or second IVF-ICSI cycle between January 2015 and December 2019 in a tertiary referral hospital.

Participants/materials, setting, methods

PCOS phenotype was based on hyperandrogenism (H), ovulatory dysfunction (O) and PCO-like ovarian morphology (P). Ovarian stimulation was performed with rFSH or HPhMG, adjusted to BMI. The primary outcome was cumulative live birth rate (CLBR) resulting from the transfer of all cryopreserved embryos from the same IVF-ICSI cycle. Patient and cycle characteristics and laboratory and clinical data were analysed. Data were analysed by multivariate logistic regression adjusting for covariates.

Main results and the role of chance

In total, 91/422 (21.6%) patients had PCOS phenotype A (HOP); 33 (7.8%) had phenotype C (HP), 161/422 (38.2%) had phenotype D (OP) and 137/422 (32.5%) had PCOM (n = 137). BMI, AMH and AFC were significantly different between phenotype groups (p &lt; 0.001), and highest in PCOS phenotype A. The type of gonadotropin used, as well as the mean daily and total stimulation dose were comparable for all groups. The mean number of retrieved oocytes was comparable among groups (22.4±10.8 for phenotype A, 21.4±7.1 for phenotype C, 20.4±7.8 for phenotype D and 22.2±9.7 for PCOM; p = 0.46). The mean number of embryos available for vitrification differed significantly (4.4±3.7, 5.7±3.4, 5.7±3.4 and 5.2±3.6, respectively; p = 0.005). Following the first frozen embryo transfer, LBR was comparable among groups (41.5%, 43.3%, 49.3% and 38.5%, respectively; p = 0.31). Unadjusted CLBR was also similar (69.2%, 69.7%, 79.5% and 67.9%, respectively; p = 0.11). The multivariate logistic regression model adjusting for age, BMI, number of oocytes and embryo stage (cleavage vs. blastocyst stage) confirmed that the PCOS/PCOM phenotype did not have any impact on CLBR (OR 0.80, CI 0.28-2.29 (phenotype C); OR 1.40, CI 0.67-2.90 (phenotype D); OR 0.65, CI 0.31-1.34 (PCOM); p = 0.1, with phenotype A as reference).

Limitations, reasons for caution

These data should be interpreted with caution as the retrospective nature of the study holds the possibility of unmeasured confounding factors. The results cannot be generalised to all ART cycles in women with polycystic ovaries as they pertain to those cycles where OS leads to hyperresponse.

Wider implications of the findings

In subfertile women with PCOS eligible for ART, hyperresponse after OS confers excellent cumulative live birth rates when a freeze-all strategy is used, eliminating unfavourable clinical outcomes that had previously been observed in hyperandrogenic PCOS women after mild OS targeting normal ovarian response and fresh embryo transfer.

Trial registration number

not applicable

P–619 Oral dydrogesterone (OD) versus micronized vaginal progesterone (MVP) for luteal phase support (LPS) in IVF/ICSI: a double blind, cross-over, pharmacokinetic study

Study question

How does the blood pharmacokinetic (PK) profile of OD/MVP differ after the first and last administration dose when used as LPS for fresh embryo transfer? Summary answer: The PK profile differed strongly between both LPS administration strategies with a more rapid absorption, metabolism and clearance of OD in comparison with MVP.

What is known already

Adequate LPS is crucial to achieve a successful pregnancy following ovarian stimulation (OS) and fresh embryo transfer. OD has been proven to be non-inferior compared to MVP in two phase III clinical trials. Additionally, a combined individual participant data and aggregate data meta-analysis showed an odds ratio in favor of OD for live birth. Little information is available on the PK of LPS strategies, leaving an important field unexplored. Individualization of LPS has recently gained more interest and insight into the PK of progestogens is essential to correctly interpret the potential impact of circulating hormone levels on reproductive outcomes.

Study design, size, duration

Twenty oocyte donors underwent two OS cycles followed by one week of LPS (OD or MVP) in a randomized, cross-over, double blind, double dummy fashion. As both dydrogesterone (D) and 20αdihydrodydrogesterone (DHD) are progestogenic, D, DHD and progesterone (P) plasma levels were established using a validated liquid chromatography tandem mass spectrometry assay in each cycle, on the 1st (single dose PK) and 8th day (multiple dose PK) of LPS (9 and 12 harvesting time-points, respectively).

Participants/materials, setting, methods

All oocyte donors were &lt;35 years, had regular menstrual cycles, no intra-uterine contraceptive device, AMH within normal range and BMI ≤ 29 kg/m2. OS was performed in a GnRH antagonist protocol followed by dual triggering (1000U hCG + 0.2mg triptorelin) as soon as ≥ 3 follicles of 20mm were present. Following oocyte retrieval, subjects initiated LPS consisting of MVP 200 mg (Utrogestan®) or OD 10 mg (Duphaston®), both three times daily.

Main results and the role of chance

The mean (±SD) age of the subjects was 27.4 (± 3.8) years and BMI was 24.0 (±3.2) kg/m2. The mean (±SD) number of oocytes retrieved was 19.7 ±10. No adverse events were reported during the intake of the study medication. The PK results are best estimates as sampling was reduced compared to a formal PK study. Following the intake of the first dose of OD, the observed maximal plasma concentrations (Cmax) for D and DHD were 2.9 and 77 ng/ml (single dose). The Cmax for D and DHD was reached after 1.5 and 1.6 hours (=Tmax), respectively. On the 8th day of LPS the first administration of that day gave rise to a Cmax of 3.6 and 88 ng/ml for D and DHD (multiple dose). For both, the observed Tmax was 1.5 hours. Following the intake of the first dose of MVP, the Cmax for P was 16 ng/mL with a Tmax of 4.2 hours. On the 8th day of LPS the first administration of that day showed a Cmax for P of 21 ng/mL with a Tmax of 7.3 hours. Although low, the role of chance could be influenced by the relatively low sampling numbers and frequency.

Limitations, reasons for caution

Peripheral concentrations do not necessarily reflect the steroidogenic effect on endometrial progesterone receptors. Extrapolation to clinical practice is therefore difficult, however, molecular analyses of endometrial tissue harvested within this study protocol are underway to investigate further pharmacodynamics and the progestogenic impact on endometrial receptivity during the embryo implantation period.

Wider implications of the findings: This is the first study comparing OD/MVP pharmacokinetics in IVF/ICSI. Results suggest administration frequency to be as important as dose, definitely for OD, showing a rapid absorption/clearance. More studies are needed to investigate blood levels in relation to time of LPS administration, especially in (artificially prepared) FET and LPS individualization.

Trial registration number

EUDRACT 2018–000105–23

Early pregnancy loss in patients with polycystic ovary syndrome after IVM versus standard ovarian stimulation for IVF/ICSI

STUDY QUESTION

Is the incidence of early pregnancy loss (EPL) in patients with polycystic ovary syndrome (PCOS) higher after IVM of oocytes than after ovarian stimulation (OS) for IVF/ICSI?

SUMMARY ANSWER

Women with PCOS who are pregnant after fresh embryo transfer have a higher probability of EPL following IVM, but after frozen embryo transfer (FET), no significant difference in the incidence of EPL was observed following IVM compared to OS.

WHAT IS KNOWN ALREADY

There is conflicting evidence in the current literature with regard to the risk of EPL after IVM of oocytes when compared with OS. Because of the limited sample size in previous studies, the use of different IVM systems and the possible bias introduced by patient characteristics and treatment type, firm conclusions cannot be drawn.

STUDY DESIGN, SIZE, DURATION

This was a retrospective cohort study evaluating 800 women, with a diagnosis of infertility and PCOS as defined by Rotterdam criteria, who had a first positive pregnancy test after fresh or FET following IVM or OS between January 2010 and December 2017 in a tertiary care academic medical centre.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pregnancies after non-hCG triggered IVM following a short course of highly purified human menopausal gonadotropin were compared with those after conventional OS. The primary outcome was EPL, defined as a spontaneous pregnancy loss before 10 weeks of gestation.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 329 patients with a positive pregnancy test after IVM and 471 patients with a positive pregnancy test after OS were included. Women who were pregnant after IVM were younger (28.6 ± 3.4 years vs 29.3 ± 3.6 years, P = 0.005) and had higher serum anti-Mullerian hormone levels (11.5 ± 8.1 ng/ml vs 7.2 ± 4.1 ng/ml, P < 0.001) compared to those who were pregnant after OS. The distribution of PCOS phenotypes was significantly different among women in the IVM group compared to those in the OS group and women who were pregnant after OS had previously suffered EPL more often (28% vs 17.6%, P = 0.003). EPL was significantly higher after fresh embryo transfer following IVM compared to OS (57/122 (46.7%) vs 53/305 (17.4%), P < 0.001), while the results were comparable after FET (63/207 (30.4%) vs 60/166 (36.1%), respectively, P = 0.24). In the multivariate logistic regression analysis evaluating fresh embryo transfer cycles, IVM was the only independent factor (adjusted odds ratio (aOR) 4.24, 95% CI 2.44-7.37, P < 0.001)) significantly associated with increased odds of EPL. On the other hand, when the same model was applied to FET cycles, the type of treatment (IVM vs OS) was not significantly associated with EPL (aOR 0.73, 95% CI 0.43-1.25, P = 0.25).

LIMITATIONS, REASONS FOR CAUTION

The current data are limited by the retrospective nature of the study and the potential of bias due to unmeasured confounders.

WIDER IMPLICATIONS OF THE FINDINGS

The increased risk of EPL after fresh embryo transfer following IVM may point towards inadequate endometrial development in IVM cycles. Adopting a freeze-all strategy after IVM seems more appropriate. Future studies are needed to ascertain the underlying cause of this observation.

STUDY FUNDING/COMPETING INTEREST(S)

The Clinical IVM research has been supported by research grants from Cook Medical and Besins Healthcare. All authors declared no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

The freeze-all strategy versus agonist triggering with low-dose hCG for luteal phase support in IVF/ICSI for high responders: a randomized controlled trial

STUDY QUESTION

Does the freeze-all strategy in high-responders increase pregnancy rates and improve safety outcomes when compared with GnRH agonist triggering followed by low-dose hCG intensified luteal support with a fresh embryo transfer?

SUMMARY ANSWER

Pregnancy rates after either fresh embryo transfer with intensified luteal phase support using low-dose hCG or the freeze-all strategy did not vary significantly; however, moderate-to-severe ovarian hyperstimulation syndrome (OHSS) occurred more frequently in the women who attempted a fresh embryo transfer.

WHAT IS KNOWN ALREADY

Two strategies following GnRH agonist triggering (the freeze-all approach and a fresh embryo transfer attempt using a low-dose of hCG for intensified luteal phase support) are safer alternatives when compared with conventional hCG triggering with similar pregnancy outcomes. However, these two strategies have never been compared head-to-head in an unrestricted predicted hyper-responder population.

STUDY DESIGN, SIZE, DURATION

This study included women with an excessive response to ovarian stimulation (≥18 follicles measuring ≥11 mm) undergoing IVF/ICSI in a GnRH antagonist suppressed cycle between 2014 and 2017. Our primary outcome was clinical pregnancy at 7 weeks after the first embryo transfer. Secondary outcomes included live birth and the development of moderate-to-severe OHSS.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Following GnRH agonist triggering, women were randomized either to cryopreserve all good-quality embryos followed by a frozen embryo transfer in an subsequent artificial cycle or to perform a fresh embryo transfer with intensified luteal phase support (1500 IU hCG on the day of oocyte retrieval, plus oral estradiol 2 mg two times a day, plus 200 mg of micronized vaginal progesterone three times a day).

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 212 patients (106 in each arm) were recruited in the study, with three patients (one in the fresh embryo transfer group and two in the freeze-all group) later withdrawing their consent to participate in the study. One patient in the freeze-all group became pregnant naturally (clinical pregnancy diagnosed 38 days after randomization) prior to the first frozen embryo transfer. The study arms did not vary significantly in terms of the number of oocytes retrieved and embryos produced/transferred. The intention to treat clinical pregnancy and live birth rates (with the latter excluding four cases lost to follow-up: one in the fresh transfer and three in the freeze-all arms, respectively) after the first embryo transfer did not vary significantly among the fresh embryo transfer and freeze-all study arms: 51/105 (48.6%) versus 57/104 (54.8%) and 41/104 (39.4%) versus 42/101 (41.6%), respectively (relative risk for clinical pregnancy 1.13, 95% CI 0.87-1.47; P = 0.41). However, moderate-to-severe OHSS occurred solely in the group that received low-dose hCG (9/105, 8.6%, 95% CI 3.2% to 13.9% vs 0/104, 95% CI 0 to 3.7, P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

The sample size calculation was based on a 19% absolute difference in terms of clinical pregnancy rates, therefore smaller differences, as observed in the trial, cannot be reliably excluded as non-significant.

WIDER IMPLICATIONS OF THE FINDINGS

This study offers the first comparative analysis of two common strategies applied to women performing IVF/ICSI with a high risk to develop OHSS. While pregnancy rates did not vary significantly, a fresh embryo transfer with intensified luteal phase support may still not avoid the risk of moderate-to-severe OHSS and serious consideration should be made before recommending it as a routine first-line treatment. Future trials may allow us to confirm these findings.

STUDY FUNDING/COMPETING INTEREST(S)

The authors have no conflicts of interest to disclose. No external funding was obtained for this study.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier NCT02148393.

TRIAL REGISTRATION DATE

28 May 2014.

DATE OF FIRST PATIENT’S ENROLMENT

30 May 2014.

The proliferative phase endometrium in IVF/ICSI: an in-cycle molecular analysis predictive of the outcome following fresh embryo transfer

STUDY QUESTION

Does an early proliferative phase endometrial biopsy harvested during ovarian stimulation harbour information predictive of the outcome following fresh embryo transfer (ET) in that same cycle?

SUMMARY ANSWER

Transcriptome analysis of the whole-tissue endometrium did not reveal significant differential gene expression (DGE) in relation to the outcome; however, the secretome profile of isolated, cultured and in vitro decidualized endometrial stromal cells (EnSCs) varied significantly between patients who had a live birth compared to those with an implantation failure following fresh ET in the same cycle as the biopsy.

WHAT IS KNOWN ALREADY

In the majority of endometrial receptivity research protocols, biopsies are harvested during the window of implantation (WOI). This, however, precludes ET in that same cycle, which is preferable as the endometrium has been shown to adapt over time. Endometrial biopsies taken during ovarian stimulation have been reported not to harm the chances of implantation, and in such biopsies DGE has been observed between women who achieve pregnancy versus those who do not. The impact of the endometrial proliferative phase on human embryo implantation remains unclear, but deserves further attention, especially since in luteal phase endometrial biopsies, a transcriptional signature predictive for repeated implantation failure has been associated with reduced cell proliferation, possibly indicating proliferative phase involvement. Isolation, culture and in vitro decidualization (IVD) of EnSCs is a frequently applied basic research technique to assess endometrial functioning, and a disordered EnSC secretome has previously been linked with failed implantation.

STUDY DESIGN, SIZE, DURATION

This study was nested in a randomized controlled trial (RCT) investigating the effect of endometrial scratching during the early follicular phase of ovarian stimulation on clinical pregnancy rates after IVF/ICSI. Of the 96 endometrial biopsies available, after eliminating those without fresh ET and after extensive matching in order to minimize the risk of potential confounding, 18 samples were retained to study two clinical groups: nine biopsies of patients with a live birth versus nine biopsies of patients with an implantation failure, both following fresh ET performed in the same cycle as the biopsy. We studied the proliferative endometrium by analysing its transcriptome and by isolating, culturing and decidualizing EnSCs in vitro. We applied this latter technique for the first time on proliferative endometrial biopsies obtained during ovarian stimulation for in-cycle outcome prediction, in an attempt to overcome inter-cycle variability.

PARTICIPANTS/MATERIALS, SETTING, METHODS

RNA-sequencing was performed for 18 individual whole-tissue endometrial biopsies on an Illumina HiSeq1500 machine. DGE was analysed three times using different approaches (DESeq2, EdgeR and the Wilcoxon rank-sum test, all in R). EnSC isolation and IVD was performed (for 2 and 4 days) for a subset of nine samples, after which media from undifferentiated and decidualized cultures were harvested, stored at -80°C and later assayed for 45 cytokines using a multiplex suspension bead immunoassay. The analysis was performed by partial least squares regression modelling.

MAIN RESULTS AND THE ROLE OF CHANCE

After correction for multiple hypothesis testing, DGE analysis revealed no significant differences between endometrial samples from patients who had a live birth and those with an implantation failure following fresh ET. However secretome analysis after EnSC isolation and culture, showed two distinct clusters that clearly corresponded to the two clinical groups. Upon IVD, the secretome profiles shifted from that of undifferentiated cells but the difference between the two clinical groups remained yet were muted, suggesting convergence of cytokine profiles after decidualization.

LIMITATIONS, REASONS FOR CAUTION

Caution is warranted due to the limited sample size of the study and the in vitro nature of the EnSC experiment. Validation on a larger scale is necessary, however, hard to fulfil given the very limited availability of in-cycle proliferative endometrial biopsies outside a RCT setting.

WIDER IMPLICATIONS OF THE FINDINGS

These data support the hypothesis that the endometrium should be assessed not only during the WOI and that certain endometrial dysfunctionalities can probably be detected early in a cycle by making use of the proliferative phase. This insight opens new horizons for the development of endometrial tests, whether diagnostic or predictive of IVF/ICSI treatment outcome.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Fonds Wetenschappelijk Onderzoek (FWO, Flanders, Belgium, 11M9415N, 1 524 417N), Wetenschappelijk Fonds Willy Gepts (WFWG G160, Universitair Ziekenhuis Brussel, Belgium) and the National Medicine Research Council (NMRC/CG/M003/2017, Singapore). There are no conflicts of interests.

TRIAL REGISTRATION NUMBER

NCT02061228.

To trigger or not to trigger ovulation in a natural cycle for frozen embryo transfer: a randomized controlled trial

STUDY QUESTION

Is the clinical pregnancy rate (CPR) following a frozen embryo transfer (FET) in a natural cycle (NC) higher after spontaneous ovulation than after triggered ovulation [natural cycle frozen embryo transfer (NC-FET) versus modified NC-FET]?

SUMMARY ANSWER

The CPR did not vary significantly between the two FET preparation protocols.

WHAT IS KNOWN ALREADY

Although the use of FET is continuously increasing, the most optimal endometrial preparation protocol is still under debate. For transfer in the NC specifically, conflicting results have been reported in terms of the outcome following spontaneous or triggered ovulation.

STUDY DESIGN, SIZE, DURATION

In a tertiary hospital setting, subjects were randomized with a 1:1 allocation into two groups between January 2014 and January 2019. Patients in group A underwent an NC-FET, while in group B, a modified NC-FET was performed with a subcutaneous hCG injection to trigger ovulation. In neither group was additional luteal phase support administered. All embryos were vitrified-warmed on Day 3 and transferred on Day 4 of embryonic development. The primary outcome was CPR at 7 weeks. All patients were followed further until 10 weeks of gestation when the ongoing pregnancy rate (OPR) was defined by the observation of foetal cardiac activity on ultrasound scan. Other secondary outcomes included biochemical pregnancy rate, early pregnancy loss and the number of visits, blood samples and ultrasonographic examinations prior to FET.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 260 patients (130 per study arm) were randomized, of whom 12 withdrew consent after study arm allocation. A total of 3 women conceived spontaneously before initiating the study cycle and 16 did not start for personal or medical reasons. Of the 229 actually commencing monitoring for the study FET cycle, 7 patients needed to be switched to a hormonal replacement treatment protocol due to the absence of follicular development, 12 had no embryo available for transfer after warming and 37 had a spontaneous LH surge before the ovulation trigger could be administered, although they were allocated to group B. Given the above, an intention-to-treat (ITT) analysis was performed taking into account 248 patients (125 in group A and 123 in group B), as well as a per protocol (PP) analysis on a subset of 173 patients (110 in group A and 63 in group B).

MAIN RESULTS AND THE ROLE OF CHANCE

Demographic features were evenly distributed between the study groups, as were the relevant fresh and frozen ET cycle characteristics. According to the ITT analysis, the CPR and OPR in group A (33.6% and 27.2%, respectively) and group B (29.3% and 24.4%, respectively) did not vary significantly [relative risk (RR) 0.87, 95% CI (0.60;1.26), P = 0.46 and RR 0.90, 95% CI (0.59;1.37), P = 0.61, respectively]. Biochemical pregnancy rate and early pregnancy loss were also found to be not statistically significantly different between the groups. In contrast, more clinic visits and blood samplings for cycle monitoring were required in the NC-FET group (4.05 ± 1.39) compared with the modified NC-FET group (3.03 ± 1.16, P = <0.001), while the number of ultrasound scans performed were comparable (1.70 ± 0.88 in group A versus 1.62 ± 1.04 in group B). The additional PP analysis was in line with the ITT results: CPR in group A was 36.4% versus 38.1% in group B [RR 1.05, 95% CI (0.70;1.56), P = 0.82].

LIMITATIONS, REASONS FOR CAUTION

The results are limited by the high drop-out rate for the PP analysis in the modified NC-FET group as more than one-third of the subjects allocated to this group ovulated spontaneously before ovulation triggering. Nonetheless, this issue is inherent to routine clinical practice and is an important observation of an event that can only be avoided by performing a very extensive monitoring that limits the practical advantages associated with modified NC-FET. Furthermore, although this is the largest randomized controlled trial (RCT) investigating this specific research question so far, a higher sample size would allow smaller differences in clinical outcome to be detected, since currently they may be left undetected.

WIDER IMPLICATIONS OF THE FINDINGS

This RCT adds new high-quality evidence to the existing controversial literature concerning the performance of NC-FET versus modified NC-FET. Based on our results showing no statistically significant differences in clinical outcomes between the protocols, the treatment choice may be made according to the patient's and treating physician's preferences. However, the modified NC-FET strategy reduces the need for hormonal monitoring and may therefore be considered a more patient-friendly and potentially cost-effective approach.

STUDY FUNDING/COMPETING INTEREST(S)

No specific funding was available for this study. None of the authors have a conflict of interest to declare with regard to this study.

TRIAL REGISTRATION NUMBER

NCT02145819.

TRIAL REGISTRATION DATE

8 January 2014.

DATE OF FIRST PATIENT’S ENROLMENT

21 January 2014.

Outcome of in-vitro oocyte maturation in patients with PCOS: does phenotype have an impact?

STUDY QUESTION

Does the phenotype of patients with polycystic ovary syndrome (PCOS) affect clinical outcomes of ART following in-vitro oocyte maturation?

SUMMARY ANSWER

Cumulative live birth rates (CLBRs) after IVM were significantly different between distinct PCOS phenotypes, with the highest CLBR observed in patients with phenotype A/HOP (= hyperandrogenism + ovulatory disorder + polycystic ovaries), while IVM in patients with phenotype C/HP (hyperandrogenism + polycystic ovaries) or D/OP (ovulatory disorder + polycystic ovaries) resulted in lower CLBRs (OR 0.26 (CI 0.06-1.05) and OR 0.47 (CI 0.25-0.88), respectively, P = 0.03).

WHAT IS KNOWN ALREADY

CLBRs in women with hyperandrogenic PCOS phenotypes (A/HOP and C/HP) have been reported to be lower after ovarian stimulation (OS) and ART when compared to CLBR in women with a normo-androgenic PCOS phenotype (D/OP) and non-PCOS patients with a PCO-like ovarian morphology (PCOM). Whether there is an influence of the different PCOS phenotypes on success rates of IVM has been unknown.

STUDY DESIGN, SIZE, DURATION

This was a single-centre, retrospective cohort study including 320 unique PCOS patients performing their first IVM cycle between April 2014 and January 2018 in a tertiary referral hospital.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Baseline patient characteristics and IVM treatment cycle data were collected. The clinical outcomes following the first IVM embryo transfer were retrieved, including the CLBR defined as the number of deliveries with at least one live birth resulting from one IVM cycle and all appended cycles in which fresh or frozen embryos were transferred until a live birth occurred or until all embryos were used. The latter was considered as the primary outcome. A multivariate regression model was developed to identify prognostic factors for CLBR and test the impact of the patient's PCOS phenotype.

MAIN RESULTS AND THE ROLE OF CHANCE

Half of the patients presented with a hyperandrogenic PCOS phenotype (n = 140 A/HOP and n = 20 C/HP vs. n = 160 D/OP). BMI was significantly different between phenotype groups (27.4 ± 5.4 kg/m2 for A/HOP, 27.1 ± 5.4 kg/m2 for C/HP and 23.3 ± 4.4 kg/m2 for D/OP, P < 0.001). Metformin was used in 33.6% of patients with PCOS phenotype A/HOP, in 15.0% of C/HP patients and in 11.2% of D/OP patients (P < 0.001). Anti-müllerian hormone levels differed significantly between groups: 12.4 ± 8.3 µg/l in A/HOP, 7.7 ± 3.1 µg/l in C/HP and 10.4 ± 5.9 µg/l in D/OP patients (P = 0.01). The number of cumulus-oocyte complexes (COC) was significantly different between phenotype groups: 25.9 ± 19.1 COC in patients with phenotype A/HOP, 18.3 ± 9.0 COC in C/HP and 19.8 ± 13.5 COC in D/OP (P = 0.004). After IVM, patients with different phenotypes also had a significantly different number of mature oocytes (12.4 ± 9.3 for A/HOP vs. 6.5 ± 4.2 for C/HP vs. 9.1 ± 6.9 for D/OP, P < 0.001). The fertilisation rate, the number of usable embryos and the number of cycles with no embryo available for transfer were comparable between the three groups. Following the first embryo transfer, the positive hCG rate and LBR were comparable between the patient groups (44.7% (55/123) for A/HOP, 40.0% (6/15) for C/HP, 36.7% (47/128) for D/OP, P = 0.56 and 25.2% (31/123) for A/HOP, 6.2% (1/15) for C/HP, 26.6% (34/128) for D/OP, respectively, P = 0.22). However, the incidence of early pregnancy loss was significantly different across phenotype groups (19.5% (24/123) for A/HOP, 26.7% (4/15) for C/HP and 10.2% (13/128) for D/OP, P = 0.04). The CLBR was not significantly different following univariate analysis (40.0% (56/140) for A/HOP, 15% (3/20) for C/HP and 33.1% (53/160) for D/OP (P = 0.07)). When a multivariable logistic regression model was developed to account for confounding factors, the PCOS phenotype appeared to be significantly correlated with CLBR, with a more favourable CLBR in the A/HOP subgroup (OR 0.26 for phenotype C/HP (CI 0.06-1.05) and OR 0.47 for phenotype D/OP (CI 0.25-0.88), P = 0.03)).

LIMITATIONS, REASONS FOR CAUTION

These data should be interpreted with caution as the retrospective nature of the study holds the possibility of unmeasured confounding factors and misassignment of the PCOS phenotype. Moreover, the sample size for phenotype C/HP was too small to draw conclusions for this subgroup of patients.

WIDER IMPLICATIONS OF THE FINDINGS

Caucasian infertile patients with a PCOS phenotype A/HOP who undergo IVM achieved a higher CLBR than their counterparts with C/HP and D/OP. This is in strong contrast with previously reported outcomes following OS where women with PCOS and hyperandrogenism (A/HOP and C/HP) performed significantly worse. For PCOS patients who require ART, the strategy of OS followed by an elective freeze-all strategy remains to be compared with IVM in a prospective fashion; however, the current data provide support for IVM as a valid treatment option, especially in the most severe PCOS phenotypes (A/HOP). Our data suggest that proper patient selection is of utmost importance in an IVM programme.

STUDY FUNDING/COMPETING INTEREST(S)

The clinical IVM research has been supported by research grants from Cook Medical and Besins Healthcare. All authors declared no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Follicular-phase endometrial scratching: a truncated randomized controlled trial

STUDY QUESTION

Does intentional endometrial injury (scratching) during the follicular phase of ovarian stimulation (OS) increase the clinical pregnancy rate (CPR) in ART?

SUMMARY ANSWER

CPR did not vary between the endometrial injury and the control group, but the trial was underpowered due to early termination because of a higher clinical miscarriage rate observed in the endometrial injury arm after a prespecified interim analysis.

WHAT IS KNOWN ALREADY

Intentional endometrial injury has been put forward as an inexpensive clinical tool capable of enhancing endometrial receptivity. However, despite its widespread use, the benefit of endometrial scratching remains controversial, with several recent randomized controlled trials (RCTs) being unable to confirm its added value. So far, most research has focused on endometrial scratching during the luteal phase of the cycle preceding the one with embryo transfer (ET), while only a few studies investigated in-cycle injury during the follicular phase of OS. Also, the persistence of a scratch effect in subsequent treatment cycles remains unclear and possible harms have been insufficiently studied.

STUDY DESIGN, SIZE, DURATION

This RCT was performed in a tertiary hospital setting between 3 April 2014 and 8 October 2017. A total of 200 women (100 per study arm) undergoing IVF/ICSI in a GnRH antagonist suppressed cycle followed by fresh ET were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were randomized with a 1:1 allocation ratio to either undergo a pipelle endometrial biopsy between Days 6 and 8 of OS or to be in the control group.The primary outcome was CPR. Secondary outcomes included biochemical pregnancy rate, live birth rate (LBR), early pregnancy loss (biochemical pregnancy losses and clinical miscarriages), excessive procedure pain/bleeding and cumulative reproductive outcomes within 6 months of the study cycle.

MAIN RESULTS AND THE ROLE OF CHANCE

The RCT was stopped prematurely by the trial team after the second prespecified interim analysis raised safety concerns, namely a higher clinical miscarriage rate in the intervention group. The intention-to-treat CPR was similar between the biopsy and the control arm (respectively, 44 versus 40%, P = 0.61, risk difference = 3.6 with 95% confidence interval = -10.1;17.3), as was the LBR (respectively, 32 versus 36%, P = 0.52). The incidence of a biochemical pregnancy loss was comparable between both groups (10% in the intervention group versus 15% in the control, P = 0.49), but clinical miscarriages occurred significantly more frequent in the biopsy group (25% versus 8%, P = 0.032). In the intervention group, 3% of the patients experienced excessive procedure pain and 5% bleeding. The cumulative LBR taking into account all conceptions (spontaneous or following ART) within 6 months of randomization was not significantly different between the biopsy and the control group (54% versus 60%, respectively, P = 0.43).

LIMITATIONS, REASONS FOR CAUTION

The trial was stopped prematurely due to safety concerns after the inclusion of 200 of the required 360 patients. Not reaching the predefined sample size implies that definite conclusions on the outcome parameters cannot be drawn. Furthermore, the pragmatic design of the study may have limited the detection of specific subgroups of women who may benefit from endometrial scratching.

WIDER IMPLICATIONS OF THE FINDINGS

Intentional endometrial injury during the follicular phase of OS warrants further attention in future research, as it may be harmful. These findings should be taken in consideration together with the growing evidence from other RCTs that scratching may not be beneficial.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by 'Fonds Wetenschappelijk Onderzoek' (FWO, Flanders, Belgium, 11M9415N, 1524417N). None of the authors have a conflict of interest to declare with regard to this study.

The mechanism of action of oxytocin antagonist nolasiban in ART in healthy female volunteers

RESEARCH QUESTION

What are the effects of the oxytocin receptor (OTR) antagonist nolasiban on uterine contractions, endometrial perfusion and endometrial mRNA expression?

DESIGN

Randomized, double-blind, parallel-group, mechanism-of-action study with nolasiban. Forty-five healthy, pre-menopausal women were treated with placebo, 900 mg or 1800 mg nolasiban on the day corresponding to blastocyst transfer. Ultrasonographic uterine contraction frequency and endometrial perfusion were assessed, and endometrial biopsies analysed by next-generation sequencing.

RESULTS

Both doses of nolasiban showed decreased contraction frequency and increased endometrial perfusion depending on the time point assessed. At 1800 mg, 10 endometrial genes (DPP4, CNTNAP3, CNTN4, CXCL12, TNXB, CTSE, OLFM4, KRT5, KRT6A, IDO2) were significantly differentially expressed (adjusted P < 0.05). Of these, OLFM4, DPP4 and CXCL12 were regulated in the same direction as genes involved in implantation during the window of implantation. In addition, three genes (DPP4, CXCL12 and IDO2) were associated with decidualization and endometrial receptivity.

CONCLUSIONS

These data expand our knowledge of the mechanism of action of nolasiban in increasing pregnancy rates after embryo transfer. The results suggest more marked effects of nolasiban 1800 mg compared with the 900 mg dose, supporting testing at higher doses in IVF patients.

IVF in women aged 43 years and older: a 20-year experience

RESEARCH QUESTION

What are the reproductive outcomes of women aged 43 years and older undergoing IVF and intracytoplasmic sperm injection (ICSI) treatment using their own eggs.

DESIGN

Retrospective study of 833 woman aged 43 years or older undergoing their first IVF and ICSI cycle using autologous oocytes at a tertiary referral hospital between January 1995 and December 2019. Live birth rate (LBR) after 24 weeks' gestation was the primary outcome.

RESULTS

Ninety-five out of 833 (11.4%) had a positive HCG, whereas 59 (62.1% per positive HCG) had a miscarriage before 12 weeks' gestation and 36 (4.3%) live births were achieved. Analysis by age showed that the number of cumulus-oocyte complexes retrieved was significantly different between the four age groups: 43 years (5 [3-9]); 44 years (5 [2-7]); 45 years (3 [2-8)]); ≥45 years (2.5 [2-6]); P < 0.01; the number of metaphase II oocytes, however, was similar. Positive HCG rates remained low: 43 years (78/580 [13.4%]); 44 years (14/192 [7.3%]); 45 years (1/39 [2.6%]; and ≥46 years (2/22 [9.1%]); P = 0.03, as did LBR: 43 years (28 [4.8%]); 44 (7 [3.6%]); 45 years (0 [0%]); and ≥46 years (1 [4.5%]); P = 0.5. Multivariate regression analysis revealed that only number of metaphase II was significantly associated with LBR, when age was considered as a continuous (OR 1.08, 96% CI 1.004 to 1.16) or categorical variable (OR 1.08, 95% CI 1.005 to 1.16).

CONCLUSION

The chances of achieving a live birth in patients aged 43 years and older undergoing IVF/ICSI with their own gametes are low, even in cases of patients with a relatively 'normal' ovarian reserve for their age.

Predicting suboptimal oocyte yield following GnRH agonist trigger by measuring serum LH at the start of ovarian stimulation

STUDY QUESTION

Are the LH levels at the start of ovarian stimulation predictive of suboptimal oocyte yield from GnRH agonist triggering in GnRH antagonist down-regulated cycles?

SUMMARY ANSWER

LH levels at the start of ovarian stimulation are an independent predictor of suboptimal oocyte yield following a GnRH agonist trigger.

WHAT IS KNOWN ALREADY

A GnRH agonist ovulation trigger may result in an inadequate oocyte yield in a small subset of patients. This failure can range from empty follicle syndrome to the retrieval of much fewer oocytes than expected. Suboptimal response to a GnRH agonist trigger has been defined as the presence of circulating LH levels <15 IU/l 12 h after triggering. It has been shown that patients with immeasurable LH levels on trigger day have an up to 25% risk of suboptimal response.

STUDY DESIGN, SIZE, DURATION

In this retrospective cohort study, all patients (n = 3334) who received GnRH agonist triggering (using Triptoreline 0.2 mg) for final oocyte maturation undergoing a GnRH antagonist cycle in our centre from 2011 to 2017 were included. The primary outcome of the study was oocyte yield, defined as the ratio between the total number of collected oocytes and the number of follicles with a mean diameter >10 mm prior to GnRH agonist trigger.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The endocrine profile of all patients was studied at initiation as well as at the end of ovarian stimulation. In order to evaluate whether LH levels, not only at the end but also at the start, of ovarian stimulation predicted oocyte yield, we performed multivariable regression analysis adjusting for the following confounding factors: female age, body mass index, oral contraceptives before treatment, basal and trigger day estradiol levels, starting FSH levels, use of highly purified human menopausal gonadotrophin and total gonadotropin dose. Suboptimal response to GnRH agonist trigger was defined as <10th percentile of oocyte yield.

MAIN RESULTS AND THE ROLE OF CHANCE

The average age was 31.9 years, and the mean oocyte yield was 89%. The suboptimal response to GnRH agonist trigger cut-off (<10th percentile) was 45%, which was exhibited by 340 patients. Following confounder adjustment, multivariable regression analysis showed that LH levels at the initiation of ovarian stimulation remained an independent predictor of suboptimal response even in the multivariable model (adjusted OR 0.920, 95% CI 0.871-0.971). Patients with immeasurable LH levels at the start of stimulation (<0.1 IU/l) had a 45.2% risk of suboptimal response, while the risk decreased with increasing basal LH levels; baseline circulating LH <0.5 IU/L, <2 IU/L and <5 IU/L were associated with a 39.1%, 25.2% and 13.6% risk, respectively.

LIMITATIONS, REASONS FOR CAUTION

The main limitation of the study is its retrospective design.

WIDER IMPLICATIONS OF THE FINDINGS

This is the largest study of GnRH agonist trigger cycles only, since most of the previous research on the predictive value of basal LH levels was performed in dual trigger cycles. LH values should be measured prior to start of ovarian stimulation. In cases where they are immeasurable, suboptimal response to GnRH agonist trigger can be anticipated, and an individualized approach is warranted.

STUDY FUNDING/COMPETING INTEREST(S)

There was no funding and no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Frozen-warmed blastocyst transfer after 6 or 7 days of progesterone administration: impact on live birth rate in hormone replacement therapy cycles

OBJECTIVE

To study the difference in live birth rate (LBR) between frozen-warmed blastocyst transfer (FET) on the 6th or the 7th day of progesterone administration in artificially prepared cycles.

DESIGN

Retrospective cohort study.

SETTING

Tertiary university-based referral hospital.

PATIENT(S)

Patients who underwent FET between December 2015 and December 2017 in a hormone replacement therapy cycle (HRT).

INTERVENTION(S)

Group A included all eligible patients who underwent transfer of a vitrified-warmed blastocyst on the 6th day of progesterone administration; group B included patients who underwent blastocyst transfer on the 7th day of progesterone. The artificial HRT protocol in this study consisted of estrogen administration at a dose of 2 mg twice daily for 7 days followed by 2 mg three times daily for 6 days and micronized vaginal progesterone 200 mg three times daily from an adequately considered endometrial thickness onward.

MAIN OUTCOME MEASURE(S)

Live birth rate.

RESULTS

The study included 619 patients, 346 in group A and 273 in group B. The LBRs were comparable between both groups (36.6% for group A and group B), even after adjustment for confounding factors (adjusted odds ratio 1.073, 95% confidence interval 0.740-1.556). Subgroup analysis revealed significantly higher miscarriage rates for day 6 blastocysts transferred on the 6th day of progesterone supplementation compared with transfer on the 7th day of progesterone supplementation (50.0% versus 21.4%, respectively). Additionally, there was a tendency toward a higher LBR when the 7-day progesterone supplementation protocol was used for transfer of a day 6 blastocyst (21.5% and 35.5% for group A and group B, respectively).

CONCLUSION

Warmed blastocyst transfer on the 6th compared with the 7th day of progesterone administration in an HRT cycle results in similar LBR. Subgroup analysis of day 6 blastocysts showed significantly higher miscarriage rates when FET was performed on the 6th day of progesterone administration.

Identification and evaluation of the microbiome in the female and male reproductive tracts

BACKGROUND

The existence of an extensive microbiome in and on the human body has increasingly dominated the scientific literature during the last decade. A shift from culture-dependent to culture-independent identification of microbes has occurred since the emergence of next-generation sequencing (NGS) techniques, whole genome shotgun and metagenomic sequencing. These sequencing analyses have revealed the presence of a rich diversity of microbes in most exposed surfaces of the human body, such as throughout the reproductive tract. The results of microbiota analyses are influenced by the technical specifications of the applied methods of analyses. Therefore, it is difficult to correctly compare and interpret the results of different studies of the same anatomical niche.

OBJECTIVES AND RATIONALE

The aim of this narrative review is to provide an overview of the currently used techniques and the reported microbiota compositions in the different anatomical parts of the female and male reproductive tracts since the introduction of NGS in 2005. This is crucial to understand and determine the interactions and roles of the different microbes necessary for successful reproduction.

SEARCH METHODS

A search in Embase, Medline Ovid, Web of science, Cochrane and Google scholar was conducted. The search was limited to English language and studies published between January 2005 and April 2018. Included articles needed to be original microbiome research related to the reproductive tracts.

OUTCOMES

The review provides an extensive up-to-date overview of current microbiome research in the field of human reproductive medicine. The possibility of drawing general conclusions is limited due to diversity in the execution of analytical steps in microbiome research, such as local protocols, sampling methods, primers used, sequencing techniques and bioinformatic pipelines, making it difficult to compare and interpret results of the available studies. Although some microbiota are associated with reproductive success and a good pregnancy outcome, it is still unknown whether a causal link exists. More research is needed to further explore the possible clinical implications and therapeutic interventions.

WIDER IMPLICATIONS

For the field of reproductive medicine, determination of what is a favourable reproductive tract microbiome will provide insight into the mechanisms of both unsuccessful and successful human reproduction. To increase pregnancy chances with live birth and to reduce reproduction-related health costs, future research could focus on postponing treatment or conception in case of the presence of unfavourable microbiota and on the development of therapeutic interventions, such as microbial therapeutics and lifestyle adaptations.