Spontaneous ovulation versus HCG triggering for timing natural-cycle frozen-thawed embryo transfer: a randomized study

Does hCG-trigger in the mild stimulation protocol for endometrial preparation have any effect on pregnancy outcome in frozen-thawed embryo transfer?

BACKGROUND

Recent literature has explored the role of human chorionic gonadotropin (hCG) triggering in frozen embryo transfer (FET) cycles with natural endometrial preparation. Despite this, the impact of hCG triggering on pregnancy outcomes following endometrial preparation with mild stimulation (mST) using Letrozole and Gonadotropins remains inadequately characterized. This study aimed to elucidate the effects of hCG-trigger on pregnancy outcomes in mST-FET cycles.

METHODS

In the present retrospective cohort study, the pregnancy outcomes of 409 eligible patients who underwent FET cycles with endometrial preparation using a mild ovarian stimulation protocol by letrozole plus low dose gonadotropins at the Royan Institute between 2020 and 2022, were investigated. The study population were segregated into two distinct groups according to type of ovulation: the spontaneous ovulation group (n = 138) and the hCG-trigger group (n = 271). The pregnancy outcomes including implantation and clinical pregnancy rates (CPR) and live birth rates (LBR) were compared between two groups. The multivariable logistic regression was performed to detect the most significant variables related to the LBR in the mST-FET cycles.

RESULTS

Demographic and baseline characteristics were comparable between groups. No significant difference was found in terms of implantation rate (0.65 ± 0.32 vs. 0.60 ± 0.30, P-value: 0.31), CPR (37% vs. 39.7%, P-value: 0.53), and LBR (35.5% vs. 37.3%, P-value: 0.74) in the spontaneous ovulation and hCG-trigger groups, respectively. The logistic regression analysis revealed that only the stage of the transferred embryo exhibited a significant relationship with LBR (blastocyst vs. cleavage: odds ratio (OR); 2.33, 95% confidence interval (CI):1.41-3.86, P-value = 0.001).

CONCLUSION

Pregnancy outcomes in the mST-FET cycles, including implantation rate, CPR, and LBR are comparable in cycles with or without hCG triggering. Based on the findings from multivariate regression analysis, the sole significant predictive factor for the LBR was the transfer of blastocyst embryos. It is recommended that these results be examined and discussed in future prospective studies with a larger sample size, considering the lack of comparable research in this field.

Use of hCG for luteal support in natural frozen-thawed blastocyst transfer cycles: a cohort study

Introduction

In the realm of natural frozen-thawed embryo transfer (FET) cycles, the application of luteal phase support (LPS) is a prevalent practice, primarily due to its beneficial impact on reproductive outcomes. Among the various LPS medications, human chorionic gonadotropin (hCG) is one that exerts its function on both the corpus luteum and the endometrium.

Objective

To evaluate the effect of hCG administration as LPS on reproductive outcomes in natural FET cycles.

Methods

This study was a retrospective cohort analysis conducted at a tertiary care hospital. It included women who underwent natural FET treatment from January 2018 to December 2022. Participants were divided into the hCG LPS group and the non-hCG LPS group on the basis of whether they used hCG as LPS after blastocyst transfer. The primary outcome was the clinical pregnancy and live birth rates. The secondary outcomes included the early miscarriage rate (before 12th gestational week) and total miscarriage rate.

Results

A total of 4762 women were included in the analysis, and 1910 received hCG LPS and 2852 received no hCG LPS (control group). In the general cohort, the clinical pregnancy and live birth rates in the hCG LPS group were significantly lower than those in the control group (63.82% vs 66.41%, aOR 0.872, 95% CI 0.765-0.996, P=0.046; 53.98% vs 57.15%, aOR 0.873, 95% CI 0.766-0.991, P=0.035, respectively). The early miscarriage and total miscarriage rates were similar between the two groups. In a subgroup analysis, in women who received an hCG trigger, there was no significant difference in the clinical pregnancy rate or live birth rate between the two groups. However, in women who ovulated spontaneously, the clinical pregnancy and live birth rates in the hCG LPS group were significantly lower than those in the control group (60.99% vs 67.21%, aOR 0.786, 95% CI 0.652-0.946, P=0.011; 50.56% vs 57.63%, aOR 0.743, 95% CI 0.619-0.878, P=0.001, respectively).

Conclusion

Among women undergoing natural cycle frozen-thawed blastocyst transfer, hCG LPS is associated with lower clinical pregnancy and live birth rates. Additionally, the adverse effect of hCG LPS is more pronounced in women who ovulate spontaneously.

Ideal frozen embryo transfer regime

PURPOSE OF REVIEW

This review aims to compare evidence on four criteria (embryo implantation, obstetric outcomes, patient convenience, and IVF-unit efficiency) by analyzing published research on different endometrial preparation methods for frozen embryo transfer (FET).

RECENT FINDINGS

While the artificial-FET cycle provides advantages in scheduling and implantation, it falls short in ensuring optimal obstetric outcomes. In contrast, natural-FET ensures embryo implantation conditions if ovulation is correctly identified. Supplementing with exogenous progesterone shields against low corpus luteum progesterone secretion, crucial for positive obstetric outcomes. In mNC-FET, ovulation is hCG-triggered, closely resembling natural cycles and reducing monitoring visits for enhanced patient convenience.Letrozole is a recommended option for anovulatory patients, preserving endometrial thickness. It is cost-effective, less likely to induce multifollicular development than gonadotropins, and better tolerated.In a novel approach, the natural-proliferative-phase-FET initiates progesterone in an unmediated ovulatory cycle at 7 mm endometrial thickness, combining the benefits of a natural proliferative endometrium with the convenience of scheduled artificial cycles.

SUMMARY

The artificial cycle offers scheduling advantages, but may compromise obstetric outcomes. Natural FET relies on accurate ovulation timing for successful implantation. mNC-FET simplifies the process using hCG induction, minimizing clinic visits for improved convenience. Letrozole is highlighted as a cost-effective and well tolerated option in anovulatory patients. A recent innovative approach combines elements of natural and artificial cycles, showing promise for FET procedures.

Home-based monitoring of ovulation to time frozen embryo transfers in the Netherlands (Antarctica-2): an open-label, nationwide, randomised, non-inferiority trial

BACKGROUND

The growing field of assisted reproductive techniques, including frozen-thawed embryo transfer (FET), should lead the way to the best sustainable health care without compromising pregnancy chances. Correct timing of FET is crucial to allow implantation of the thawed embryo. Nowadays, timing based on hospital-controlled monitoring of ovulation in the natural cycle of a woman is the preferred strategy because of the assumption of favourable fertility prospects. However, home-based monitoring is a simple method to prevent patient travel and any associated environmental concerns. We compared ongoing pregnancy rates after home-based monitoring versus hospital-controlled monitoring with ovulation triggering.

METHODS

This open-label, multicentre, randomised, non-inferiority trial was undertaken in 23 hospitals and clinics in the Netherlands. Women aged between 18 and 44 years with a regular ovulatory menstrual cycle were randomly assigned in a 1:1 ratio via a web-based randomisation program to home-based monitoring or hospital-controlled monitoring. Those who analysed the data were masked to the groups; those collecting the data were not. All endpoints were analysed by intention to treat and per protocol. Non-inferiority was established when the lower limit of the 90% CI exceeded -4%. This study was registered at the Dutch Trial Register (Trial NL6414).

FINDINGS

1464 women were randomly assigned between April 10, 2018, and April 13, 2022, with 732 allocated to home-based monitoring and 732 to hospital-controlled monitoring. Ongoing pregnancy occurred in 152 (20·8%) of 732 in the home-based monitoring group and in 153 (20·9%) of 732 in the hospital-controlled monitoring group (risk ratio [RR] 0·99 [90% CI 0·81 to 1·22]; risk difference [RD] -0·14 [90% CI -3·63 to 3·36]). The per-protocol analysis confirmed non-inferiority (152 [21·0%] of 725 vs 153 [21·0%] of 727; RR 1·00 (90% CI 0·81 to 1·23); RD -0·08 [90% CI -3·60 to 3·44]).

INTERPRETATION

Home-based monitoring of ovulation is non-inferior to hospital-controlled monitoring of ovulation to time FET.

FUNDING

The Dutch Organisation for Health Research and Development.

Natural Cycle Frozen Embryo Transfer: Evaluating Optimal Protocols for Preparation and Timing

Background

While natural cycle frozen embryo transfer (NC-FET) is becoming increasingly common, significant practice variation exists in the use of ovulation induction medications, administration of ovulation trigger, and timing of embryo transfer without consensus as to the optimal protocol.

Aims

The objective of this study is to evaluate the association of key aspects of the NC-FET protocol with implantation, pregnancy and live birth.

Settings and Design

This was a retrospective cohort study of blastocyst stage NC-FET cycles from October 2019 to July 2021 at a single academic fertility centre.

Materials and Methods

Protocols varied between cycles across three key parameters which were evaluated as primary predictors of cycle outcomes: (1) use of letrozole for mild ovarian stimulation/ovulation induction, (2) administration of exogenous ovulation trigger versus spontaneous luteinising hormone surge and (3) transfer timing based on ovulation trigger versus sequential progesterone monitoring. Primary outcomes included implantation rate, clinical pregnancy and ongoing pregnancy.

Statistical Analysis Used

Generalised estimating equations were fitted to obtain adjusted odds ratios or rate ratios as appropriate with 95% confidence intervals for each outcome across the three primary predictors.

Results

A total of 183 cycles from 170 unique patients were eligible for inclusion. The average implantation rate was 0.58, resulting in an overall clinical pregnancy and ongoing pregnancy rate of 59.0% and 51.4%, respectively. After adjusting for age at embryo freeze and history of a failed embryo transfer, there were no significant associations between any predictor and implantation rate, clinical pregnancy, ongoing pregnancy, or live birth.

Conclusion

In NC-FET, a variety of preparation and timing protocols may lead to comparable cycle outcomes, potentially allowing for flexibility on the basis of patient and physician preference. These findings warrant validation in a larger, randomised trial.

Ovulatory-cycle frozen embryo transfer: spontaneous or triggered ovulation and the impact of LH elevation at hCG triggering

The effect of the luteinizing hormone (LH) elevation before the human chorionic gonadotropin (hCG) trigger in ovulatory frozen-thawed embryo transfer (Ovu-FET) cycles has not been determined. We aimed to investigate whether triggering ovulation in Ovu-FET cycles affects the live birth rate (LBR), and the contribution of elevated LH at the time of hCG trigger. This retrospective study included Ovu-FET cycles performed in our center from August 2016 to April 2021. Modified Ovu-FET (hCG trigger) and true Ovu-FET (without hCG trigger) were compared. The modified group was divided according to whether hCG was administered, before or after LH increased to > 15 IU/L and was twice the baseline value. The modified (n = 100) and true (n = 246) Ovu-FET groups and both subgroups of the modified Ovu-FET, those who were triggered before (n = 67) or after (n = 33) LH elevation, had comparable characteristics at baseline. Comparison of true vs. modified Ovu-FET outcomes revealed similar LBR (35.4% vs. 32.0%; P = 0.62), respectively. LBR were similar between the modified Ovu-FET subgroups regardless of the hCG trigger timing (31.3% before vs. 33.3% after LH elevation; P = 0.84). In conclusion, LBR of Ovu-FET were not affected by hCG trigger or whether LH was elevated at the time of hCG trigger. These results add reassurance regarding hCG triggering even after LH elevation.

The effects of unexpected follicular growth and ovulation in artificial cycles: a retrospective cohort study of frozen, single-blastocyst transfer

OBJECTIVE

To study the effects of unexpected follicular development and ovulation in artificial cycles (ACs) on pregnancy outcomes.

DESIGN

A retrospective cohort study.

SETTING

A university-affiliated fertility center.

PATIENT(S)

A total of 1,427 patients who underwent a single, frozen-thawed blastocyst transfer with AC regimens from January 2014 to December 2020 at a university-affiliated fertility center were included.

INTERVENTION(S)

Unexpected follicular development and ovulation in ACs.

MAIN OUTCOME MEASURE(S)

Live birth rate (LBR), biochemical pregnancy rate, clinical pregnancy rate, and ongoing pregnancy rate.

RESULT(S)

A total of 161 patients with unexpected follicular development and ovulation in ACs (ovulation group) and 1,266 patients without growing follicles in ACs (control group) were enrolled. The patients in the ovulation group were older and had higher levels of serum follicle-stimulating hormone and lower levels of serum antimüllerian hormone. After propensity score matching, the baseline characteristics between the 2 groups were comparable and no significant difference was observed in the LBR (ovulation group, 39.0% vs. control group, 39.0%), biochemical pregnancy rate (ovulation group, 60.3% vs. control group, 58.2%), clinical pregnancy rate (ovulation group, 53.4% vs. control group, 50.7%), or ongoing pregnancy rate (ovulation group, 42.5% vs. control group, 40.4%). Moreover, the patients in the ovulation group showed a lower risk of hypertensive disorders of pregnancy (HDP) (1.6% vs. 15.3%). A subgroup analysis of women who delivered singleton live-born babies also demonstrated that unexpected follicular development and ovulation in ACs was associated with a decreased risk of HDP (adjusted odds ratio, 0.070; 95% confidence interval, 0.007-0.712) and an increased risk of large-for-gestational-age infants (adjusted odds ratio, 4.046; 95% confidence interval, 1.319-12.414).

CONCLUSION(S)

Women with unexpected follicular development and ovulation during single frozen-thawed blastocyst transfer with AC regimens had a similar LBR and a reduced risk of HDP compared with those with routine AC regimens, and singleton neonates had an increased risk of being large for gestational age.

Premature timing of progesterone luteal phase support initiation did not negatively impact live birth rates in modified natural frozen thawed embryo transfer cycles

Study question

In a modified natural cycle frozen-thawed embryo transfer (mNC-FET), does the premature timing of progesterone luteal phase support (LPS) initiation 24 h following human chorionic gonadotropin (hCG) trigger impact live birth?

Summary answer

Premature LPS initiation did not negatively affect the live birth rate (LBR) in mNC-FET cycles compared with conventional LPS initiation 48 h after hCG triggering.

What is known already

During natural cycle FET, human chorionic gonadotropin is routinely used to mimic endogenous luteinizing hormone (LH) surge to induce ovulation, which allows more flexibility in embryo transfer scheduling, thus relieving the burden of multiple visits by patients and laboratory workloads, which is also known as mNC-FET. Moreover, recent data demonstrates that ovulatory women undergoing natural cycle FETs have a lower risk of maternal and fetal complications due to the essential role of the corpus luteum in implantation, placentation and pregnancy maintenance. While several studies have confirmed the positive effects of LPS in mNC-FETs, the timing of progesterone LPS initiation is still unclear, as compared with fresh cycles where robust research has been conducted. To the best of our knowledge, no clinical studies comparing different beginning days in mNC-FET cycles have been published.

Study design size duration

This retrospective cohort study involved 756 mNC-FET cycles performed at a university-affiliated reproductive center between January 2019 and August 2021. The primary outcome measured was the LBR.

Participants/materials setting methods

Ovulatory women ≤42 years of age who were referred for their autologous mNC-FET cycles were included in the study. According to the timing of progesterone LPS initiation following the hCG trigger, patients were assigned into two categories: premature LPS group (progesterone initiation 24 h after hCG trigger, n = 182) versus conventional LPS group (progesterone initiation 48 h after hCG trigger, n = 574). Multivariate logistic regression analysis was used to control for confounding variables.

Main results and the role of chance

There were no differences in background characteristics between the two study groups, except for the proportion of assisted hatching (53.8% in premature LPS group versus 42.3% in conventional LPS group, p = 0.007). In the premature LPS group, 56 of 182 patients (30.8%) had a live birth, compared to 179 of 574 patients (31.2%) in the conventional LPS group, with no significant difference observed between groups (adjusted odds ratio [aOR] 0.98, 95% confidence interval [CI] 0.67-1.43, p = 0.913). In addition, there was no significant difference between the two groups in other secondary outcomes. A sensitivity analysis for LBR according to the serum LH and progesterone levels on hCG trigger day also confirmed the aforementioned findings.

Limitations reasons for caution

In this study, retrospective analysis was conducted in a single center and was therefore prone to bias. Additionally, we did not anticipate monitoring the patient's follicle rupture and ovulation after hCG triggering. Future prospective clinical trials remain necessary to confirm our results.

Wider implications of the findings

While exogenous progesterone LPS was added 24 h after hCG triggering, embryo-endometrium synchrony would not be adversely affected so long as sufficient time was allowed for endometrial exposure to exogenous progesterone. Our data support promising clinical outcomes following this event. As a result of our findings, clinicians and patients will be able to make better informed decisions.

Study funding/competing interests

No specific funding was available for this study. The authors have no personal conflicting interests to declare.

Trial registration number

N/A.

Comparing the success rate of natural cycle and modified natural cycle protocols for frozen-thawed embryo transfer

Objective: The aim of the present study is to compare the effects of Natural Cycle and modified Natural Cycle protocols for frozen-thawed embryo transfer on clinical pregnancy rate and live birth rate. Methods: This prospective randomized controlled trial comprised 145 patients scheduled for frozen-thawed embryo transfer and was conducted at a university hospital between 2019 and 2021. The Natural Cycle protocol was administered to 73 patients and the modified Natural Cycle protocol to 72 patients and the clinical outcome was compared between the groups. The main outcome measure was live birth rate. Results: Baseline characteristics and cycle parameters were similar in both groups. There was no difference in clinical pregnancy rate (58.9% and 54.2%, respectively; p = .565) and live birth rate between the Natural Cycle and modified Natural Cycle groups (49.3% and 48.6% respectively; p = .932). Conclusion: This study established that clinical pregnancy and live birth rates were not affected by natural cycle ovulation being spontaneous or hCG-triggered among patients undergoing frozen-thawed embryo transfer. Thus, the protocol for natural cycle frozen-thawed embryo transfers should be chosen according to the priorities of the patient and the physician.

Is there an optimal window of time for transferring single frozen-thawed euploid blastocysts? A cohort study of 1170 embryo transfers

STUDY QUESTION

Is there an optimal window of time when the transfer of single frozen-thawed euploid blastocysts is associated with a maximal live birth rate (LBR)?

SUMMARY ANSWER

Performing a single frozen-thawed euploid blastocyst transfer at 160 ± 4 h post-hCG trigger in modified-natural frozen-thawed embryo transfer (FET) cycles was independently associated with a higher LBR as compared to transfers outside this window; however, in natural FET cycles, LBRs were comparable across a wider range of time intervals.

WHAT IS KNOWN ALREADY

There is compelling evidence for maintaining embryo-endometrial synchrony to optimize clinical outcomes following FETs, which could potentially be achieved by matching the transfer time of an embryo post-ovulation to its developmental age post-oocyte retrieval. For modified-natural cycles, ovulation is widely accepted to occur ∼40 h following the hCG trigger, whilst ovulation following spontaneous LH surge onset is thought to vary from 24 to 56 h.

STUDY DESIGN, SIZE, DURATION

This is a multicentered retrospective cohort study analyzing 1170 single frozen-thawed euploid blastocyst transfers following trophectoderm biopsy and preimplantation genetic testing (PGT) between May 2015 and February 2019. Limiting the analysis to single euploid embryo transfers allowed for a more accurate estimation of the endometrial synchrony factor by controlling for the developmental stage of the embryo (full blastocyst or more advanced) and its genetic composition. LBR per FET was the primary outcome measure.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients underwent natural or gonadotrophin-induced preparation of the endometrium, with serial serum oestradiol, LH and progesterone measurements. Optimally timed transfers were predefined as those conducted 120 ± 4 h post-ovulation since biopsy and subsequent cryopreservation of full blastocysts which is usually performed at 116-124 h post-oocyte retrieval. This was considered the equivalent of 160 ± 4 h post-hCG trigger in modified-natural cycles (n = 253), as ovulation was assumed to occur ∼40 h after the hCG trigger. For natural cycles (n = 917), this was also considered to be, on average, 160 ± 4 h post the spontaneous LH surge. Thus, study groups were determined as those with optimal timing or not, and additional exploratory and subgroup analyses were performed, varying the time window in terms of onset and width, both overall and per endometrial preparation protocol. Statistical analysis was performed using the generalized estimating equations (GEE) framework to control for the clustered nature of the data while adjusting for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, LBRs were significantly higher when the transfer had been performed at 160 ± 4 h post-hCG trigger or LH surge onset compared to when it had been performed outside this window (44.7% vs 36.0%; P = 0.008). A multivariable regression GEE model including the cycle type (natural versus modified-natural), previtrification embryo quality (top versus good quality), embryo stage (fully hatched versus hatching or earlier blastocyst), vitrification day (D5 versus D6) and survival rate (>90% versus <90%) as covariates, confirmed that, overall, embryo transfers conducted 160 ± 4 h post-hCG trigger or LH surge onset (the assumed equivalent of 120 ± 4 h post-ovulation) were associated with a significantly higher LBR (relative risk (RR) 1.21, 95% CI 1.04-1.41). Subgroup exploratory analyses per endometrial preparation protocol demonstrated that these findings were primarily present in the modified-natural cycle group (RR 1.52, 95% CI 1.15-1.99), whilst the natural cycle group showed comparable LBRs across a wider range of time intervals. Moreover, the overall LBR for the natural group (36.8%; 95% CI 33.7-39.9%) was lower than that of the modified-natural group (41.3%; 95% CI 35.4-47.1%), suggesting that there likely remains a greater potential to further optimize the timing of natural cycle embryo transfers.

LIMITATIONS, REASONS FOR CAUTION

As with all retrospective studies, the presence of residual unknown bias cannot be excluded. Additionally, patients included in this study were a selected group who underwent PGT for specific reasons and hence the results obtained might not be directly applicable to the general population or embryos that have not undergone embryo biopsy. Furthermore, the criteria utilized to interpret hormonal data from natural cycles were specifically adopted for the present study and need to be validated in further studies.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study highlight the significance of embryo-endometrial synchrony for the optimization of frozen embryo transfer outcome. However, it also clearly supports that the implantation window is in most cases wide and the achievement of live birth is possible with relatively high success rates even outside the optimal window of 160 ± 4 h post-trigger for modified-natural cycles and across a range of time intervals for natural cycles. Additionally, this study suggests that implantation rates could be further optimized in natural cycles by improving methods of assessing embryo-endometrial synchrony.

STUDY FUNDING/COMPETING INTEREST(S)

C. V. is supported by a National Health and Medical Research Council Early Career Fellowship (GNT1147154). No other funding was received for this study and there are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Frozen-thawed embryo transfer in modified natural cycles: a retrospective analysis of pregnancy outcomes in ovulatory women with vs. without spontaneous luteinizing hormone surge

Background

Timing of frozen embryo transfer (FET) in natural endometrial preparation cycles is often based on luteinizing hormone (LH) surge. However, some patients do not show spontaneous LH surge despite follicular maturation. The objective of this study was to evaluate the impact of spontaneous LH surge on pregnancy outcomes in modified natural cycles (mNC).

Methods

This retrospective analysis included 1897 FET cycles with modified natural endometrial preparation in normo-ovulatory women between January 1, 2015, to December 31, 2019, at our center: 920 cycles with spontaneous LH surge (≥ 20 IU/L) and 977 without. For cleavage embryos, FET was conducted 4 and 5 days after hCG injection in women with and without LH surge, respectively. For blastocysts, FET was conducted 6 and 7 days after hCG injection in women with and without LH surge, respectively. Multivariate regression was conducted to examine the factors associated with live birth.

Results

Live birth rate was 43.7% in patients with spontaneous LH surge vs. 43.8% in women without LH surge (P = 0.961). The two groups also had similar implantation rate (36.2% vs. 36.7%, P = 0.772), biochemical pregnancy rate (54.8% vs. 55.4%, P = 0.796) and clinical pregnancy rate (50.9% vs. 51.7%, P = 0.721). In multivariate regression, live birth was not associated with LH surge (aOR, 0.947, 95% CI, 0.769, 1.166).

Conclusion

Pregnancy outcomes were similar in mNC-FET in cycles with vs. without spontaneous LH surge if FET timing is adjusted.

Impact of different endometrial preparation protocols before frozen embryo transfer on pregnancy outcomes: a review

The use of frozen embryo transfer cycles has exponentially increased in the last few years. Optimization of endometrial preparation protocols before frozen embryo transfer is mandatory to further improve pregnancy outcomes. This review will focus on the existing literature with regard to the different available endometrial preparation protocols and their impact on pregnancy outcomes. More specifically, we will focus on programmed, natural, and stimulated frozen embryo transfer cycles. The studies performed on this topic are generally of low quality, and only a few well-performed randomized controlled trials have been published. To date, no strong evidence is available to support the use of 1 preparation method over another in terms of pregnancy outcomes. However, robust data have shown a clearly protective effect of natural frozen embryo transfer cycles against long-term obstetric complications, mainly hypertensive disorders of pregnancy and large for gestational age infants. The introduction of individualized luteal phase support in different endometrial preparation protocols is actually gaining a lot of attention and requires further investigation.

A comparison of frozen-thawed embryo transfer protocols in 2920 single-blastocyst transfers

OBJECTIVE

To assess the effect of frozen-thawed embryo transfer (FET) protocol on live-birth rate (LBR) and clinical pregnancy rate (CPR), in single-vitrified-blastocyst transfer MATERIALS AND METHODS: Retrospective cohort study with FET of a single-blastocyst embryos (n = 2920 cycles) thawed 2013-2018. FET protocols were natural cycles (NC-FET) (n = 147), artificial hormone replacement treatment cycles (HRT-FET) (n = 2645), and modified NC (mNC) with hCG triggering (n = 128). Primary outcome was LBR. Adjustment for age, embryo grade, year of freezing\thawing, infertility cause, and endometrial thickness was performed.

RESULTS

There were no significant differences between the groups with regard to female age, embryo grade, and endometrial thickness. LBR was higher in the mNC compared to HRT-FET cycles (38.3% vs. 20.9% P < 0.0001), and in the NC compared to HRT-FET cycles (34.7% vs. 20.9%, P = 0.0002). CPR was higher in the mNC compared to HRT-FET cycles (46.1% vs. 33.3% P = 0.0003), and in the NC compared to HRT-FET cycles (45.9% vs. 33.3%, P = 0.002). There was no significant difference in LBR or CPR between NC-FET and mNC-FET. Higher LBR with NC-FET and mNC-FET remained significant after adjusting for confounders (aOR 2.42, 95%CI 1.53-3.66, P < 0.0001).

CONCLUSION

The use of the convenient artificial HRT-FET cycles must be cautiously reconsidered in light of the potential negative effect on LBR when compared with natural cycle FET.

Clinical outcome of intrauterine administration of peripheral mononuclear cells or human chorionic gonadotropin in unexplained implantation failure

PROBLEM

Intrauterine administration of autologous peripheral blood mononuclear cells (PBMCs) or human chorionic gonadotropin (hCG) has been proposed to facilitate embryo implantation, while its effect on clinical outcome of women with previous implantation failure (RIF) in frozen/thawed embryo transfer (FET) cycles is still unclear.

METHOD OF STUDY

A total 523 patients having not experienced successful clinical pregnancy were enrolled in our study, including 207 repeat implantation failure (RIF) patients, and 316 patients with previous implantation failures but failed to meet the diagnostic criteria for RIF (non-RIF). Autologous PBMCs were cultured with hCG for 4 h in the hCG-activated PBMC-treated group (n = 73 in RIF patients, n = 112 in non-RIF patients), and then intrauterine administered 2 days before FET. In the hCG-treated group (n = 67 in RIF patients, n = 100 in non-RIF patients), recombinant hCG was administered 2 days before FET. The control group (n = 67 in RIF patients, n = 104 in non-RIF patients) underwent FET without intrauterine administration.

RESULTS

In RIF patients, the clinical pregnancy rate of the above three groups are 56.16%, 53.73%, and 43.28%, respectively (p = .276). The implantation rate and live birth rate showed no significant differences (p > .05). For non-RIF patients, higher clinical pregnancy rate was also seen in PBMC intrauterine group (57.15%) and hCG intrauterine group (58.00%) than controls (50.96%) but without statistical significance. There were no significant differences of implantation rate and live birth rate (p > .05).

CONCLUSION

Intrauterine administration of hCG-activated PBMC and hCG did not improve clinical outcomes for both RIF and non-RIF patients before FET embryo transfer.

Frozen Blastocyst Embryo Transfer: Comparison of Protocols and Factors Influencing Outcome

Background: Various factors, including treatment protocols, can influence the outcomes of frozen embryo transfers (FETs). The study objectives were to compare different endometrial preparation protocols of FET cycles and to evaluate the factors, including the endometrial thickness (ET), that affect outcomes. Methods: This observational cohort study involved 5037 women undergoing FETs at eight tertiary clinics in the UK between January 2016 and March 2019. The endometrial preparation protocols used were natural cycle (NC-FETs), artificial hormone support cycle with oestradiol valerate but without pituitary downregulation (AC-FETs) and artificial hormone support cycle with agonist downregulation (ACDR-FETs). Results: The mean (±SD) ages across NC-FET, AC-FET and ACDR-FET groups were 36.5 (±4.2), 35.9 (±5.0) and 36.4(±4.9) years, respectively. LBRs were comparable (40.7%, 175/430; 36.8%, 986/2658; and 36.7%, 716/1949, respectively) across the three groups. Clinical pregnancy, implantation, multiple pregnancies, miscarriage and ectopic pregnancy rates were also similar. In the regression analysis of variables including age, duration of infertility, number of embryos transferred, protocol type and endometrial thickness, age was the only significant predictor of LBRs, although its predictive ability was poor (AUC: 0.55). With the overall LBR of the study population being 37.1%, the post-test probability of a live birth at an ET of <5 mm was 0%, and at 5–5.9, 6–6.9, 7–7.9 and 8–8.9 mm, the probabilities were 16.7%, 33.8%, 36.7% and 37.7%, respectively. The LBR remained above 35% up to the 14–14.9 mm range and then declined gradually to 23% for the 17–25 mm range. Conclusions: The FET outcomes were similar for the three protocols used for endometrial preparation. The protocol type and endometrial thickness were not predictive of FET outcomes; age was the only predictive variable, despite its low predictive ability.

Adverse impact of elevated serum progesterone and luteinizing hormone levels on the hCG trigger day on clinical pregnancy outcomes of modified natural frozen-thawed embryo transfer cycles

RESEARCH QUESTION

The relationship between serum progesterone (P) and luteinizing hormone (LH) levels on the human chorionic gonadotropin (hCG) trigger day and the clinical pregnancy outcomes in modified natural frozen-thawed embryo transfer (mNC-FET) cycles are controversial.

DESIGN

This was a retrospective study of 788 mNC-FET cycles. A smooth fitting curve and threshold effect analysis was performed to identify the effect of serum P and LH levels measured on the hCG day on the clinical pregnancy rate (CPR) and live birth rate (LBR) of mNC-FET cycles.

RESULTS

The CPR and LBR decreased significantly when the LH level on the hCG day was greater than or equal to 32 IU/L. Further subgroup analysis showed that the CPR decreased significantly when the P level on the hCG day was equal to or greater than 1 ng/mL. When the P level was lower (< 1 ng/mL), the patients with an LH level greater than or equal to 32 IU/L had reduced CPR and LBR in mNC-FET cycles.

CONCLUSION

Applying the hCG trigger on a day with a higher P level (≥ 1 ng/mL) leads to a decreased CPR and LBR. hCG administration with a higher LH level (≥ 32 IU/L) also leads to a decreased CPR and LBR in mNC-FET cycles when the P level is less than 1 ng/mL.

Is Human Chorionic Gonadotropin Trigger Beneficial for Natural Cycle Frozen-Thawed Embryo Transfer?

Objective: The aim of this study is to investigate, in ovulatory patients, whether there is a difference in reproductive outcomes following frozen-thawed embryo transfer (FET) in natural cycles (NC) compared to modified natural cycles (mNC).

Methods: This retrospective cohort study, performed at the public tertiary fertility clinic, involved all infertile patients undergoing endometrial preparation prior to FET in NC and mNC from January, 2017 to November, 2020. One thousand hundred and sixty-two patients were divided into two groups: mNC group (n = 248) had FET in a NC after ovulation triggering with human chorionic gonadotropin (hCG); NC group (n = 914) had FET in a NC after spontaneous ovulation were observed. The primary outcome was live birth rate. All pregnancy outcomes were analyzed by propensity score matching (PSM) and multivariable logistic regression analyses.

Results: The NC group showed a higher live birth rate [344/914 (37.6%) vs. 68/248 (27.4%), P = 0.003; 87/240 (36.3%) vs. 66/240 (27.5%), P = 0.040] than the mNC group before and after PSM analysis. Multivariable analysis also showed mNC to be associated with a decreased likelihood of live birth compared with NC [odds ratio (OR) 95% confidence interval (CI) 0.71 (0.51–0.98), P = 0.039].

Conclusion: For women with regular menstrual cycles, NC-FET may have a higher chance of live birth than that in the mNC-FET cycles. As a consequence, it's critical to avoid hCG triggering as much as possible when FETs utilize a natural cycle strategy for endometrial preparation. Nevertheless, further more well-designed randomized clinical trials are still needed to determine this finding.

A randomized controlled trial of vaginal progesterone for luteal phase support in modified natural cycle - frozen embryo transfer

OBJECTIVE

Our aim was to study whether luteal phase support (LPS) increases the live-birth rate (LBR) in women undergoing modified natural cycle (mNC) frozen-thawed embryo transfer (FET).

METHODS

In a randomized controlled trial, conducted at a university-affiliated tertiary medical center, a total of 59 patients aged 18-45 years, underwent mNC-FET. FET was performed in mNC following ovulation triggering by hCG. Patients were randomized into two groups; The No-LPS Group included 28 women who did not receive LPS, and the LPS Group included 31 women who received vaginal progesterone for LPS. The main outcome measure was LBR.

RESULTS

Baseline demographic and clinical characteristics were comparable between the study groups. The no-LPS group and the LPS group did not differ with regard to clinical pregnancy rate (21.4% vs. 32.3%; respectively, p = .35), LBR (17.9% vs. 19.4%; respectively, p = .88), or spontaneous miscarriage rate (3.6% vs. 12.9%; respectively, p = .35). On multivariate logistic regression analysis, LPS was not associated with LBR after controlling for confounders.

CONCLUSION

The results of our study suggest that LPS after mNC-FET does not improve the reproductive outcome, and therefore, might not be necessary.C linicaltrials.gov identifier: NCT01483365.

Preparation of the Endometrium for Frozen Embryo Transfer: A Systematic Review

Despite the worldwide increase in frozen embryo transfer, the search for the best protocol to prime endometrium continues. Well-designed trials comparing various frozen embryo transfer protocols in terms of live birth rates, maternal, obstetric and neonatal outcome are urgently required. Currently, low-quality evidence indicates that, natural cycle, either true natural cycle or modified natural cycle, is superior to hormone replacement treatment protocol. Regarding warmed blastocyst transfer and frozen embryo transfer timing, the evidence suggests the 6th day of progesterone start, LH surge+6 day and hCG+7 day in hormone replacement treatment, true natural cycle and modified natural cycle protocols, respectively. Time corrections, due to inter-personal differences in the window of implantation or day of vitrification (day 5 or 6), should be explored further. Recently available evidence clearly indicates that, in hormone replacement treatment and natural cycles, there might be marked inter-personal variation in serum progesterone levels with an impact on reproductive outcomes, despite the use of the same dose and route of progesterone administration. The place of progesterone rescue protocols in patients with low serum progesterone levels one day prior to warmed blastocyst transfer in hormone replacement treatment and natural cycles is likely to be intensively explored in near future.

Effect of unplanned spontaneous follicular growth and ovulation on pregnancy outcomes in planned artificial frozen embryo transfer cycles: a propensity score matching study

STUDY QUESTION

Does unplanned spontaneous follicular growth and ovulation affect clinical outcomes after planned artificial frozen-thawed embryo transfer (AC-FET) cycles?

SUMMARY ANSWER

AC-FET and spontaneous follicular growth and ovulation events resulted in notably better pregnancy outcomes with a significantly higher implantation rate (IR), clinical pregnancy rate (CPR), ongoing pregnancy rate (OPR) and live birth rate (LBR) and a significantly lower miscarriage rate.

WHAT IS KNOWN ALREADY

The AC-FET protocol without GnRH agonist administration is associated with a low incidence of follicular growth and ovulation. In the literature, authors often refer to these types of cycles with concern due to possibly impaired FET outcomes. However, the real impact of such cycles has yet to be elucidated due to the lack of existing data.

STUDY DESIGN, SIZE, DURATION

This was a retrospective clinical study involving 2256 AC-FET cycles conducted between January 2017 and August 2019. Propensity score (PS) matching was used to control for confounding variables.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Subjects were divided into two groups: a study group: cycles with spontaneous follicular growth and ovulation (the maximum diameter of follicles in any ovary was ≥14 mm and ovulation was confirmed by consecutive ultrasound examinations) and a control group featuring cycles without growing follicles (the maximum diameter of follicles in both ovaries were <10 mm). The study group was matched by PS with the control group at a ratio of 1:2. The study group consisted of 195 patients before PS matching and 176 patients after matching. The numbers of participants in the control group before and after PS matching were 2061 and 329, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

This analysis showed that patient age (adjusted odds ratio [aOR] 1.05; 95% CI 1.01-1.09; P=0.010) and basal FSH level (aOR 1.06; 95% CI 1.01-1.11; P=0.012) were significantly and positively related with the spontaneous follicular growth and ovulation event. In addition, this event was negatively correlated with BMI (aOR 0.92; 95% CI 0.87-0.97; P=0.002), AMH level (aOR 0.66; 95% CI 0.59-0.74; P<0.001) and a high starting oestrogen dose (aOR 0.53; 95% CI 0.38-0.76 for 6 mg vs. 4 mg; P<0.001). Baseline characteristics were similar between groups after PS matching. Patients in the study group had a significantly higher IR (28.8% vs. 21.8%, P=0.016), CPR (44.9% vs. 33.4%, P=0.011), OPR (39.2% vs. 26.1%, P=0.002) and LBR (39.2% vs. 24.9%, P=0.001) and a lower miscarriage rate (12.7% vs. 25.5%, P=0.030), compared with those in the control group.

LIMITATIONS, REASONS FOR CAUTION

This was a retrospective study carried out in a single centre and was therefore susceptible to bias. In addition, we only analysed patients with normal ovulation patterns and excluded those with follicular growth but without ovulation. Further studies remain necessary to confirm our results.

WIDER IMPLICATIONS OF THE FINDINGS

It is not necessary to cancel cycles that experience spontaneous follicular growth and ovulation. Our data support promising clinical outcomes after this event. Our findings are important as they can better inform clinicians and patients.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by National Natural Science Foundation of China (grant no. 81701507, 81801404, 81871210, 82071648), Natural Science Foundation of Jiangsu Province (grant no. BK20171126, BK20201123) and Jiangsu Province '333' project. The authors declare that they have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

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.

Should women receive luteal support following natural cycle frozen embryo transfer? A systematic review and meta-analysis

BACKGROUND

Spontaneous ovulation during a natural menstrual cycle is frequently used for timing frozen embryo transfer (FET). Nevertheless, it remains unclear whether or not women should receive luteal phase support (LPS) following natural cycle frozen embryo transfer (NC-FET).

OBJECTIVE AND RATIONALE

The aim of this systematic review and meta-analysis was to study whether the administration of LPS improves the reproductive outcome following NC-FET.

SEARCH METHODS

We conducted a systematic search of the literature published in Medline/PubMed, Embase and the Cochrane Library, from January 2000 until December 2020. We included all original English, peer-reviewed articles, irrespective of the study design. The search strategy included keywords related to NC-FET and luteal phase support. Studies reporting the results of artificial or stimulated FET cycles were excluded.

OUTCOMES

Our systematic search generated 416 records. After screening, eight studies were included in the review and seven studies were included in the meta-analysis. Two studies (n = 858) used hCG and six studies (n = 1507) used progesterone for luteal support. Four studies were randomised controlled trials (RCTs), whereas the other four were historic cohort studies. In a meta-analysis using a random effects model, hCG administration for LPS did not increase the clinical pregnancy rate (CPR) (two studies, odds ratio (OR) 0.85, 95% CI 0.64-1.14). On the other hand, progesterone LPS was associated with a higher CPR (five studies, OR 1.48, 95% CI 1.14-1.94), and a higher live birth rate (LBR) (three studies, OR 1.67, 95% CI 1.19-2.36). The association between progesterone LPS and the LBR remained significant after excluding non-randomised studies.

WIDER IMPLICATIONS

The available evidence indicates that progesterone administration for LPS is beneficial following NC-FET. There is no evidence to support the administration of hCG for LPS in these cases. Additional large RCTs are necessary to improve the quality of evidence and validate our findings.

The clinical relevance of luteal phase progesterone support in true natural cycle cryopreserved blastocyst stage embryo transfers: a retrospective cohort study

Background

More than 67% of all embryos transferred in the United States involve frozen-thawed embryos. Progesterone supplementation is necessary in medicated cycles to luteinize the endometrium and prepare it for implantation, but little data is available to show if this is beneficial in true natural cycles. We evaluated the use of luteal phase progesterone supplementation for cryopreserved/warmed blastocyst transfers in true natural cycles not using an ovulatory trigger.

Methods

Retrospective cohort study in a single academic medical center. We studied the use of luteal phase progesterone supplementation in patients undergoing true natural cycle cryopreserved blastocyst embryo transfers. Our primary outcome measure was ongoing pregnancy rate, with other pregnancy outcomes being evaluated (i.e. implantation rate, miscarriage rate, ectopic rate, and multifetal gestation). Categorical data were analyzed utilizing Fisher’s exact test and all binary variables were analyzed using log-binomial regression to produce a risk ratio.

Results

Two hundred twenty-nine patients were included in the analysis with 149 receiving luteal phase progesterone supplementation and 80 receiving no luteal phase support. Patient demographic and cycle characteristics, and embryo quality were similar between the two groups. No difference was seen in ongoing pregnancy rate (49.0% vs. 47.5%, p = 0.8738), clinical pregnancy rate (50.3% vs. 47.5%, p = 0.7483), positive HCG rate (62.4% vs. 57.5%, p = 0.5965), miscarriage/abortion rate (5.4% vs. 2.5%, p = 0.2622), ectopic pregnancy rate (0% vs. 1.3%, p = 0.3493), or multifetal gestations (7.4% vs. 3.8%, p = 0.3166).

Conclusion(s)

The addition of luteal phase progesterone support in true natural cycle cryopreserved blastocyst embryo transfers did not improve pregnancy outcomes and therefore the routine use in practice cannot be recommended based on this study, but the utilization should not be discouraged without further studies.

Capsule

Progesterone supplementation as luteal phase support in true natural cycle cryopreserved blastocyst transfers does not improve ongoing pregnancies.

Should the modified natural cycle protocol for frozen embryo transfer be modified? A prospective case series proof of concept study

OBJECTIVE

Modified natural cycles for frozen embryo transfer utilize an ovulation trigger which assists in embryo transfer scheduling and simplifies cycle monitoring. There have been conflicting results with this protocol and modifications may be sought. We wanted to ascertain whether a modified natural protocol for frozen embryo transfer without triggered ovulation but with luteal progesterone support disconnecting the timing of embryo transfer from the timing of the LH surge can achieve a high pregnancy rate.

STUDY DESIGN

Candidates for frozen embryo transfer of 48-h cleavage cell embryos were recruited from May 2016 to April 2018. The patients were monitored for endometrial growth, follicle formation and estradiol, progesterone, and LH hormone levels. After meeting the predetermined criteria, embryo transfer was scheduled. The patients began progesterone treatment 48 h before embryo transfer, regardless of identification of the LH surge if ovulation had not commenced. The predetermined primary outcome was the biochemical pregnancy rate while the secondary outcome included the clinical pregnancy rate and the ongoing pregnancy rate. Patients were monitored to the eighth week of pregnancy, but data was collected from the medical records to provide the live birth rate as well.

RESULTS

Fifty-six women were screened. Eleven women declined or did not meet the inclusion criteria. Three had anovulatory cycles and were excluded. Forty-two women were included in the statistical analysis. The implantation rate was 42.9 % [95 %CI 29.3 %-56.4 %). Of the 42 participants, 25 (59.5 %) conceived [95 % CI 44.0 %-75 %]. Two pregnancies ended in first trimester miscarriage leaving 23 (54.7 %) ongoing pregnancies [95 % CI 39.1 %-70.5 %]. One patient experienced a late abortion such that the live birth rate was 22 of 42 patients or 52.4 % [95 % CI 36.4 %-68.0 %].

CONCLUSION

The proposed modified natural protocol which utilizes progesterone luteal support but does not trigger ovulation, maintains a high pregnancy rate while providing flexibility regarding the day of transfer disconnected from the day of the LH surge. This was a prospective, proof of concept study. This protocol may be suitable for smaller or public in-vitro fertility units whose resources are limited and facilities are not available daily. The high pregnancy and live birth rate that we found provides confidence that this protocol can be part of the armament of protocols the clinician may offer to his patients. Larger studies should confirm these findings.

Optimising Follicular Development, Pituitary Suppression, Triggering and Luteal Phase Support During Assisted Reproductive Technology: A Delphi Consensus

BACKGROUND

A Delphi consensus was conducted to evaluate global expert opinions on key aspects of assisted reproductive technology (ART) treatment.

METHODS

Ten experts plus the Scientific Coordinator discussed and amended statements plus supporting references proposed by the Scientific Coordinator. The statements were distributed via an online survey to 35 experts, who voted on their level of agreement or disagreement with each statement. Consensus was reached if the proportion of participants agreeing or disagreeing with a statement was >66%.

RESULTS

Eighteen statements were developed. All statements reached consensus and the most relevant are summarised here. (1) Follicular development and stimulation with gonadotropins (n = 9 statements): Recombinant human follicle stimulating hormone (r-hFSH) alone is sufficient for follicular development in normogonadotropic patients aged <35 years. Oocyte number and live birth rate are strongly correlated; there is a positive linear correlation with cumulative live birth rate. Different r-hFSH preparations have identical polypeptide chains but different glycosylation patterns, affecting the biospecific activity of r-hFSH. r-hFSH plus recombinant human LH (r-hFSH:r-hLH) demonstrates improved pregnancy rates and cost efficacy versus human menopausal gonadotropin (hMG) in patients with severe FSH and LH deficiency. (2) Pituitary suppression (n = 2 statements): Gonadotropin releasing hormone (GnRH) antagonists are associated with lower rates of any grade ovarian hyperstimulation syndrome (OHSS) and cycle cancellation versus GnRH agonists. (3) Final oocyte maturation triggering (n=4 statements): Human chorionic gonadotropin (hCG) represents the gold standard in fresh cycles. The efficacy of hCG triggering for frozen transfers in modified natural cycles is controversial compared with LH peak monitoring. Current evidence supports significantly higher pregnancy rates with hCG + GnRH agonist versus hCG alone, but further evidence is needed. GnRH agonist trigger, in GnRH antagonist protocol, is recommended for final oocyte maturation in women at risk of OHSS. (4) Luteal-phase support (n = 3 statements): Vaginal progesterone therapy represents the gold standard for luteal-phase support.

CONCLUSIONS

This Delphi consensus provides a real-world clinical perspective on the specific approaches during the key steps of ART treatment from a diverse group of international experts. Additional guidance from clinicians on ART strategies could complement guidelines and policies, and may help to further improve treatment outcomes.

Is there a critical LH level for hCG trigger after the detection of LH surge in modified natural frozen-thawed single blastocyst transfer cycles?

Purpose

There is no consensus yet in the literature on an optimal luteinizing hormone (LH) level for human chorionic gonadotrophin (hCG) trigger timing in patients undergoing frozen-thawed embryo transfer (FET) with modified natural cycles (mNC). The objective of our study was to compare the clinical results of hCG trigger at different LH levels in mNC-FET cases.

Methods

This retrospective study was conducted in Istanbul Memorial Hospital ART and Genetics Center. A total of 1076 cases with 1163 mNC-FET cycles were evaluated. LH levels between the start of LH rise (15 IU/L) and LH peak level (> 40 IU/L) were evaluated. Cycles were analyzed in four groups: group A (n = 287) LH level on the day prior to the day of hCG; groups B, C and D, LH levels on the day of hCG: group B (n = 245) LH 15–24.9; group C (n = 253), LH 25–39.9; group D (n = 383) LH ≥ 40. Cycle outcomes in the four groups were compared.

Results

Subgroup analyses of mNC-FET groups showed that implantation, clinical and ongoing pregnancy rates, and pregnancy losses were not significantly different in patients with different LH levels on the day of hCG trigger.

Conclusion

Our study suggests that hCG can be administered at any time between the start of LH rise (≥ 15 IU/L) and LH peak level (≥ 40 IU/L) without a detrimental effect on clinical outcome.

Clinical Outcomes of Frozen-Thawed Embryo Transfer in Natural Cycles with Spontaneous or Induced Ovulation: a Retrospective Cohort Study from 1937 Cycles

Our objective was to assess whether there is a difference in the pregnancy outcomes in the natural cycle (NC) with spontaneous LH rise compared with modified natural cycle controlled by hCG for final oocyte maturation and ovulation after frozen-thawed embryo transfer (FET). In this retrospective cohort study, we analyzed the clinical outcomes of a total of 1937 patients undergoing FET followed by endometrial preparation with the natural cycle and modified natural cycle. The primary outcome was live birth, and secondary outcomes included miscarriage rate, clinical pregnancy rate, preterm birth rate, and ectopic pregnancy rate. The type of endometrial preparation did not impact live birth (adjusted odds ratio [aOR] 0.92; 95% confidence interval [CI], 0.69-1.23), miscarriage (aOR 0.83; 95%CI, 0.50-1.39), clinical pregnancy (aOR 0.88; 95%CI, 0.66-1.18), preterm birth (aOR 0.91; 95%CI, 0.56-1.50), or ectopic pregnancy (aOR 1.06; 95%CI, 0.29-3.94). In conclusion, in women undergoing FET, natural cycles and modified natural cycles resulted in comparable clinical outcomes.

A UK-wide cross-sectional survey of practice exploring current trends in endometrial preparation for frozen-thawed embryo replacement

In the United Kingdom, between 2012 and 2017 the annual number of frozen-thawed embryo replacement (FER) cycles doubled, while fresh cycles declined. With FER now accounting for 34% of IVF cycles, the aim of this UK-wide survey of IVF clinics was to determine current trends in the management of FER. A senior clinician in each of the 84 UK IVF clinics was asked to complete an online survey between September 2018 and February 2019 focussing on their clinic's first-line protocols for FER. Sixty-five clinics (77%) responded, accounting for approximately 24,419 FER cycles annually. In ovulatory women, 69% of clinics favour medicated, 26% natural cycle and 5% modified natural cycle FER. In medicated FER, 61% of clinics undertake blastocyst transfer on the sixth day of progesterone administration, 21% on the fifth, 13% on the seventh, 3% on the fourth and 2% on the third. The preferred route of progesterone in medicated FER is vaginal, favoured by 82% of clinics. For pituitary suppression, 55% of clinics favour GnRH-agonist, 11% GnRH-antagonist and 34% oestrogen-only. In natural cycle FER, 31% always, 44% sometimes and 25% never give supplementary luteal support. In summary, the results illustrate wide variation in practice and highlight key research priorities.

Natural frozen embryo transfer with hCG booster leads to improved cycle outcomes: a retrospective cohort study

PURPOSE

To determine whether luteal support with intramuscular injection of human chorionic gonadotropin 1 day post-LH surge in natural cycle frozen embryo transfer (nFETs) increases ongoing pregnancy rates (OPR).

METHODS

Retrospective cohort study of women who underwent natural cycle FET with transfer of a single day-5 or - 6 euploid blastocyst between January 2017 and December 2018 at an academic medical center were divided into two groups based on whether they received hCG 1 day post-LH surge. Patients with uterine factor infertility were excluded.

RESULTS

A total of 529 nFET cycles were included. The OPR was significantly higher in the treatment group than in the non-treatment group when controlling for potential confounders such as embryo morphology (69.9% versus 57.4%, p = 0.0119, aOR1.724, 95% CI 1.13-2.65). There were no significant differences observed in the rates of first trimester loss (aOR 1.05, 95% CI 0.032-2.96) or biochemical pregnancy (aOR 0.79, 95% CI 0.31-1.76). Odds ratios were adjusted for patient's age, body mass index, peak endometrial thickness, gravidity, and parity.

CONCLUSION

The current data suggest that the hCG booster given to patients within 1 day post-LH surge results in improved cycle outcomes compared to patients who do not receive the booster.

Comparison of stimulated versus modified natural cycles for endometrial preparation prior to frozen embryo transfer: a randomized controlled trial

RESEARCH QUESTION

To compare stimulated cycle (STC) versus modified natural cycle (MNC) for endometrial preparation prior to frozen embryo transfer (FET) in terms of convenience and efficacy.

DESIGN

Prospective, open-label, randomized controlled study including 119 patients aged 20-38 years, undergoing intra-conjugal IVF/intracytoplasmic sperm injection, having regular cycles, at least two day 2 or day 3 frozen embryos, for whom it was the first or second FET performed, randomized to either MNC (n = 59) or STC (n = 60). Monitoring consisted of ultrasound and hormonal measurements. The number of monitoring visits required was compared between the two groups.

RESULTS

STC required a significantly lower number of monitoring visits compared with MNC (3.6 ± 0.9 versus 4.4 ± 1.1, respectively, P < 0.0001), a lower number of blood tests (2.7 ± 0.8 versus 3.5 ± 1.0, respectively, P < 0.0001) and of ultrasounds (1.2 ± 0.4 versus 1.5 ± 0.6, respectively, P = 0.0039). FET during 'non-opening' hours (22.6% versus 27.5%, respectively, P = 0.32) and cancellation rates (11.7% versus 11.9%, respectively, P = 0.97) were comparable between the STC and MNC groups. No difference concerning HCG-positive rates (34.0% versus 23.1%, respectively, P = 0.22) nor live birth rates (24.5% for STC versus 23.1% for MNC, respectively, P = 0.86) was observed. Quality of life as defined by the FertiQol score was not different (P > 0.05 for each item).

CONCLUSION

Altogether, these findings can be used for everyday clinical practice to better inform patients when deciding on the protocol to use for FET. These results suggest that MNC is a good option for patients reluctant to have injections, but requires increased monitoring. STC may offer more flexibility for patients and IVF centres.

Seven Years of Vitrified Blastocyst Transfers: Comparison of 3 Preparation Protocols at a Single ART Center

Introduction: Frozen-thawed embryo transfers (FET) have become a standard practice to increase cumulative pregnancy rates, however, the choice of the best preparation protocol remains a matter of debate. Design: Retrospective analysis of clinical pregnancy (CPR) and live birth rate (LBR) of FET in natural cycles (NC-FET), modified natural cycles with hCG-triggered ovulation (mNC-FET), and hormonal artificial replacement (AR-FET). Materials and Methods: For natural cycles, patients were monitored by ultrasound to evaluate the dominant follicle and by urinary LH kits (NC-FET). When the endometrial thickness reached at least 7 mm and the dominant follicle 16-20 mm, hCG was administered in absence of urinary LH surge (mNC-FET). Embryo thawing and transfer was planned 7 days after LH surge or hCG administration. For the AR-FET, oral estradiol valerate was administered from day 2 of menstrual cycle until endometrial thickness reached at least 7 mm and transfer was planned after 5 days of vaginal progesterone start. Only single vitrified blastocyst transfers were included. Results: In total 2,895 transfers were performed of which 561 (19.4%) carried out with NC-FET, 1,749 (60.4%) with mNC-FET and 585 (20.2%) with AR-FET. CPRs were 32.62, 43.05, and 37.26%, respectively. LBR were 24.06, 33.56, and 25.81%, respectively. A statistically significant (p < 0.001) higher LBR for mNC-FET vs. NC-FET (OR 0.49-0.78) and AR-FET (OR 0.47-0.74) was observed. A higher ectopic pregnancy rate (p = 0.002) was observed in NC-FET (3.28%) than in AR-FET (1.83%) and mNC-FET (0.40%). A higher abortion rate (p = 0.031) in pregnancies <12 weeks was observed in AR-FET (27.52%) than in NC-FET (19.67%) and in mNC-FET (19.39%). At Post hoc analysis only female age (OR 0.91-0.95), antimullerian hormone (AMH) (OR 1.01-1.07) and mNC-FET (OR 1.39-1.98) were statically significant prognostic factors for LBRs. Conclusions: These results demonstrate a superior CPR and LBR following FET in hCG-triggered ovulation cycles compared to NC and AR-FET, a higher ectopic pregnancy rate in NC-FET and a higher abortion rate in pregnancies <12 weeks in AR-FET. However, these data need to be confirmed in randomized and prospective studies before definitive conclusions can be drawn. Clinicaltrials.gov ID: NCT03581422.

Modified natural-cycle cryopreserved embryo transfer: is a washout period needed after a failed fresh cycle?

RESEARCH QUESTION

Are the characteristics of the natural cycle or modified natural cycle (mNC), or live birth rates (LBR), affected by delaying frozen embryo transfer (FET) after a failed fresh IVF cycle?

DESIGN

In a retrospective study, conducted at a university-affiliated tertiary centre, 198 women aged 18-45 years undergoing their first FET cycle after a failed fresh embryo transfer attempt using an mNC were evaluated. Cycles were divided according to the time interval between oocyte retrieval and the start of the FET cycle into the immediate FET group (<22 days) and the delayed FET group (≥22 days). The main outcome measures were ovulation day and LBR.

RESULTS

The mean interval between oocyte retrieval and the start of the FET cycle was 15.6 ± 3.2 days in the immediate FET group and 84.8 ± 73.7 days in the delayed FET group (P < 0.001). Ovulation day was significantly delayed in the immediate FET group (day 17.1 ± 4.4 versus day 15.4 ± 3.7; P = 0.004). There was no difference between the immediate and delayed FET groups in terms of clinical pregnancy rate (CPR) (25.4% and 25.0%, respectively) or LBR (21.2% and 20.0%, respectively).

CONCLUSIONS

Natural-cycle characteristics are similar in immediate and delayed cycles, except for a slight delay in ovulation day. Deferring mNC-FET after a failed fresh IVF cycle does not improve the reproductive outcome. These results should encourage patients and clinicians who want to proceed with FET immediately after failure of fresh IVF.

Live birth rates after different endometrial preparation methods in frozen cleavage-stage embryo transfer cycles: a randomized controlled trial

PURPOSE

This study aimed to compare the clinical outcomes in different endometrial preparation methods prior to frozen embryo transfer (FET) in women with normal menstrual cycles.

METHODS

A total of 471 eligible patients were randomly allocated into four groups of endometrial preparation prior to FET: natural cycle with spontaneous ovulation (n = 120), natural cycle with human chorionic gonadotropin (hCG) for ovulation induction (n = 117), hormone replacement cycle (HRC) (n = 113) and HRC with pre-treatment with GnRH-a (n = 121). Natural cycle with hCG also received hCG in luteal phase. The primary outcome was live birth rate. The secondary outcomes included implantation, biochemical and clinical pregnancy, ongoing pregnancy, and late miscarriage rates. Data analysis included t test, ANOVA and χ².

RESULTS

There were no statistically significant differences in the mean age (p = 0.31), duration (p = 0.43) and cause of infertility (p = 0.77) and the number (p = 0.33) and quality (p = 0.21) of embryos transferred between the groups. No significant differences regarding the implantation rates per embryo transfer (p = 0.97) and biochemical pregnancy rates (p = 0.90) were observed between the groups. The rates of clinical pregnancy were 34.2%, 32.5%, 31% and 36.4% in the natural cycle, natural with hCG, HRC and HRC with GnRH-a groups, respectively (p = 0.83). Ongoing pregnancy (p = 0.89) and miscarriage (p = 0.33) rates were comparable between groups. The rate of live birth was 30.8% in the natural group, 30% in the natural with hCG, 27.4% in the HRC and 31.4% in the HRC with GnRH-a groups (p = 0.91).

CONCLUSION

Four different types of endometrial preparation methods for FET cycles appear to be equally effective in terms of implantation, pregnancy, miscarriage and live birth rates in women with normal menstrual cycles.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02251925.

Natural cycle versus hormone replacement therapy cycle in frozen-thawed embryo transfer

OBJECTIVES

To compare implantation rates, clinical pregnancy rates and live birth rates associated with natural and hormone replacement therapy (HRT) methods of endometrial preparation in frozen-thawed embryo transfer (FET) cycles.  Methods: The results of 108 natural cycles and 224 HRT cycles of FET transfers performed in a private in vitro fertilization (IVF) center between June 2013 and August 2015 were  retrospectively compared with respect to implantation rate, clinical pregnancy rate, and live birth rate. Results: A total of 144 embryos were transferred in 108 natural cycles and 357 embryos were  transferred in 224 HRT cycles. No statistically significant differences were found in the implantation rate (p=0.796), clinical pregnancy rate per cycle (p=0.900), clinical pregnancy rate per transferred embryo (p=0.283), live birth rate per cycle (p=0.821), or live birth rate per transferred embryo (p=0.481) between the 2 groups.  Conclusion: This study showed no difference between the implantation rate, clinical pregnancy rate or live birth rate between the natural cycle group and HRT cycle group. These results may provide clinicians with more freedom to individualize patient treatment, particularly with respect to the selection of the endometrial preparation method, if these results are supported by large randomized controlled studies in the future.

[Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG]

OBJECTIVE

To compare frozen-thawed embryo transfer (FET) outcomes in natural cycles according to ovulation induction: spontaneous versus recombinant human chorionic gonadotrophin (r-hCG) triggering.

METHODS

This retrospective study included all patients monitored for natural cycle FET during one year. When serial monitoring were performed until spontaneous LH rise, patients were included in group A (n=38) whereas those receiving r-hCG for ovulation triggering formed group B (n=43). All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. No luteal phase support had been given. We compared outcomes between the 2 groups.

RESULTS

After checking groups comparability, we didn't find significant difference for the implantation rate, clinical pregnancy rate and live birth (31% vs 45%, 32% vs 51% et 21% vs 32%, respectively for group A and B). The number of monitoring was significantly lower in group B (1,9±0,8 versus 2,5±1, P=0,006).

DISCUSSION

Although no consensus has been yet established, natural cycle seems indicated for normo-ovulating patients but the question of ovulation induction is still debated. In our study, triggering ovulation by r-hCG, respecting strict criteria, seems provide good results while reducing both protocol's constraints and cost.

HCG administration after endogenous LH rise negatively influences pregnancy rate in modified natural cycle for frozen-thawed euploid blastocyst transfer: a pilot study

PURPOSE

The aim of the present study was to evaluate whether in a modified natural cycle (modified-NC) for a frozen-thawed single euploid blastocyst transfer, a critical LH value, above which human chorionic gonadotropin (hCG) administration should be avoided, may be defined.

METHODS

One hundred and sixty-seven patients underwent modified natural cycle in order to transfer a single frozen-thawed euploid blastocyst. All embryos were obtained by intracytoplasmic sperm injection and were biopsied at the blastocyst stage and analyzed by means of array comparative genomic hybridization (aCGH). Ovulation was induced using 10.000 IU hCG when the mean follicle diameter was at least of 17 mm, independently from LH values. The primary end points were the hCG-positive test and clinical pregnancy. The interim analysis showed that LH value ≥ 13 mIU/ml on the day of hCG injection may negatively influence the clinical results, suggesting that in this condition, it should be advisable waiting for spontaneous ovulation.

RESULTS

Among patients who received hCG for ovulation induction, the hCG-positive test and clinical pregnancy rates in modified-NC were significantly lower in cycles with LH ≥ 13 mIU/ml in respect to those with LH < 13 mIU/ml (45.4 vs 73.3 and 36.4 vs 65.9%, in LH ≥ 13 and LH < 13 groups, respectively). In patients with LH value ≥ 13 mIU/ml, hCG administration led to significantly lower rates of hCG-positive test (45.4 vs 74.5% in hCG administration and spontaneous ovulation groups, respectively) and clinical pregnancy (36.4 vs 64.7% in hCG administration and spontaneous ovulation groups, respectively). The baseline patient characteristics were comparable in all groups.

CONCLUSIONS

The findings of this study highlight that LH elevation ≥ 13 mIU/ml prior to hCG administration may negatively affect clinical pregnancy rates in modified-NC for single euploid blastocyst transfer. The LH determination should be routinely performed during follicular monitoring. In the presence of LH level ≥ 13 mIU/ml, hCG administration should be avoided, and the embryo transfer should be planned only after spontaneous follicular rupture.

Frozen embryo transfer: a review on the optimal endometrial preparation and timing

STUDY QUESTION

What is the optimal endometrial preparation protocol for a frozen embryo transfer (FET)?

SUMMARY ANSWER

Although the optimal endometrial preparation protocol for FET needs further research and is yet to be determined, we propose a standardized timing strategy based on the current available evidence which could assist in the harmonization and comparability of clinic practice and future trials.

WHAT IS KNOWN ALREADY

Amid a continuous increase in the number of FET cycles, determining the optimal endometrial preparation protocol has become paramount to maximize ART success. In current daily practice, different FET preparation methods and timing strategies are used.

STUDY DESIGN, SIZE, DURATION

This is a review of the current literature on FET preparation methods, with special attention to the timing of the embryo transfer.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Literature on the topic was retrieved in PubMed and references from relevant articles were investigated until June 2017.

MAIN RESULTS AND THE ROLE OF CHANCE

The number of high quality randomized controlled trials (RCTs) is scarce and, hence, the evidence for the best protocol for FET is poor. Future research should compare both the pregnancy and neonatal outcomes between HRT and true natural cycle (NC) FET. In terms of embryo transfer timing, we propose to start progesterone intake on the theoretical day of oocyte retrieval in HRT and to perform blastocyst transfer at hCG + 7 or LH + 6 in modified or true NC, respectively.

LIMITATIONS REASONS FOR CAUTION

As only a few high quality RCTs on the optimal preparation for FET are available in the existing literature, no definitive conclusion for benefit of one protocol over the other can be drawn so far.

WIDER IMPLICATIONS OF THE FINDINGS

Caution when using HRT for FET is warranted since the rate of early pregnancy loss is alarmingly high in some reports.

STUDY FUNDING/COMPETING INTEREST(S)

S.M. is funded by the Research Fund of Flanders (FWO). H.T. and C.B. report grants from Merck, Goodlife, Besins and Abbott during the conduct of the study.

TRIAL REGISTRATION NUMBER

Not applicable.

Cycle regimens for frozen-thawed embryo transfer

BACKGROUND

Among subfertile couples undergoing assisted reproductive technology (ART), pregnancy rates following frozen-thawed embryo transfer (FET) treatment cycles have historically been found to be lower than following embryo transfer undertaken two to five days following oocyte retrieval. Nevertheless, FET increases the cumulative pregnancy rate, reduces cost, is relatively simple to undertake and can be accomplished in a shorter time period than repeated in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) cycles with fresh embryo transfer. FET is performed using different cycle regimens: spontaneous ovulatory (natural) cycles; cycles in which the endometrium is artificially prepared by oestrogen and progesterone hormones, commonly known as hormone therapy (HT) FET cycles; and cycles in which ovulation is induced by drugs (ovulation induction FET cycles). HT can be used with or without a gonadotrophin releasing hormone agonist (GnRHa). This is an update of a Cochrane review; the first version was published in 2008.

OBJECTIVES

To compare the effectiveness and safety of natural cycle FET, HT cycle FET and ovulation induction cycle FET, and compare subtypes of these regimens.

SEARCH METHODS

On 13 December 2016 we searched databases including Cochrane Gynaecology and Fertility's Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO and CINAHL. Other search sources were trials registers and reference lists of included studies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing the various cycle regimens and different methods used to prepare the endometrium during FET.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. Our primary outcomes were live birth rates and miscarriage.

MAIN RESULTS

We included 18 RCTs comparing different cycle regimens for FET in 3815 women. The quality of the evidence was low or very low. The main limitations were failure to report important clinical outcomes, poor reporting of study methods and imprecision due to low event rates. We found no data specific to non-ovulatory women. 1. Natural cycle FET comparisons Natural cycle FET versus HT FETNo study reported live birth rates, miscarriage or ongoing pregnancy.There was no evidence of a difference in multiple pregnancy rates between women in natural cycles and those in HT FET cycle (odds ratio (OR) 2.48, 95% confidence interval (CI) 0.09 to 68.14, 1 RCT, n = 21, very low-quality evidence). Natural cycle FET versus HT plus GnRHa suppressionThere was no evidence of a difference in rates of live birth (OR 0.77, 95% CI 0.39 to 1.53, 1 RCT, n = 159, low-quality evidence) or multiple pregnancy (OR 0.58, 95% CI 0.13 to 2.50, 1 RCT, n = 159, low-quality evidence) between women who had natural cycle FET and those who had HT FET cycles with GnRHa suppression. No study reported miscarriage or ongoing pregnancy. Natural cycle FET versus modified natural cycle FET (human chorionic gonadotrophin (HCG) trigger)There was no evidence of a difference in rates of live birth (OR 0.55, 95% CI 0.16 to 1.93, 1 RCT, n = 60, very low-quality evidence) or miscarriage (OR 0.20, 95% CI 0.01 to 4.13, 1 RCT, n = 168, very low-quality evidence) between women in natural cycles and women in natural cycles with HCG trigger. However, very low-quality evidence suggested that women in natural cycles (without HCG trigger) may have higher ongoing pregnancy rates (OR 2.44, 95% CI 1.03 to 5.76, 1 RCT, n = 168). There were no data on multiple pregnancy. 2. Modified natural cycle FET comparisons Modified natural cycle FET (HCG trigger) versus HT FETThere was no evidence of a difference in rates of live birth (OR 1.34, 95% CI 0.88 to 2.05, 1 RCT, n = 959, low-quality evidence) or ongoing pregnancy (OR 1.21, 95% CI 0.80 to 1.83, 1 RCT, n = 959, low-quality evidence) between women in modified natural cycles and those who received HT. There were no data on miscarriage or multiple pregnancy. Modified natural cycle FET (HCG trigger) versus HT plus GnRHa suppressionThere was no evidence of a difference between the two groups in rates of live birth (OR 1.11, 95% CI 0.66 to 1.87, 1 RCT, n = 236, low-quality evidence) or miscarriage (OR 0.74, 95% CI 0.25 to 2.19, 1 RCT, n = 236, low-quality evidence) rates. There were no data on ongoing pregnancy or multiple pregnancy. 3. HT FET comparisons HT FET versus HT plus GnRHa suppressionHT alone was associated with a lower live birth rate than HT with GnRHa suppression (OR 0.10, 95% CI 0.04 to 0.30, 1 RCT, n = 75, low-quality evidence). There was no evidence of a difference between the groups in either miscarriage (OR 0.64, 95% CI 0.37 to 1.12, 6 RCTs, n = 991, I² = 0%, low-quality evidence) or ongoing pregnancy (OR 1.72, 95% CI 0.61 to 4.85, 1 RCT, n = 106, very low-quality evidence).There were no data on multiple pregnancy. 4. Comparison of subtypes of ovulation induction FET Human menopausal gonadotrophin(HMG) versus clomiphene plus HMG HMG alone was associated with a higher live birth rate than clomiphene combined with HMG (OR 2.49, 95% CI 1.07 to 5.80, 1 RCT, n = 209, very low-quality evidence). There was no evidence of a difference between the groups in either miscarriage (OR 1.33, 95% CI 0.35 to 5.09,1 RCT, n = 209, very low-quality evidence) or multiple pregnancy (OR 1.41, 95% CI 0.31 to 6.48, 1 RCT, n = 209, very low-quality evidence).There were no data on ongoing pregnancy.

AUTHORS' CONCLUSIONS

This review did not find sufficient evidence to support the use of one cycle regimen in preference to another in preparation for FET in subfertile women with regular ovulatory cycles. The most common modalities for FET are natural cycle with or without HCG trigger or endometrial preparation with HT, with or without GnRHa suppression. We identified only four direct comparisons of these two modalities and there was insufficient evidence to support the use of either one in preference to the other.

Impact of Endometrial Preparation Protocols for Frozen Embryo Transfer on Live Birth Rates

BACKGROUND

It has been reported that a natural cycle (NC) is similar to or even better than hormone replacement therapy (HRT) in patients with regular cycles who undergo frozen embryo transfer (FET). Hundreds of FETs are managed yearly in our clinic. Scheduling these cycles is critical in a busy unit like ours. This is why we have to prove if a NC really shows a better outcome than other endometrium preparation protocols.

METHODS

Hence we carried out a prospective study between June 2011 and June 2012, which included 530 patients (570 FET cycles) randomly allocated to two study groups: Group 1 (n=280 cycles), artificial cycle (HRT); or group 2 (n=290 cycles), natural cycle. Natural cycles were later divided into two groups: 169 patients scheduled with human chorionic gonadotropin (hCG) and 121 with endogenous luteinizing hormone (LH) surge. The inclusion criteria were: age <39 years, regular menstrual cycles (26-35 days), and previous IVF cycle with embryo cryopreservation. The exclusion criteria were polycystic ovarian syndrome and endometriosis stage III/IV.

RESULTS

No statistical differences were found in the baseline characteristics among groups, nor between implantation or ongoing pregnancy rates (30.8% HRT group; 32.7% hCG group; 34.5% LH surge group). However, a higher miscarriage rate was observed in the HRT group when compared to hCG or LH surge (21.2% versus 12.9% versus 11.1%, P<0.01). Live birth rates were similar among groups, as were perinatal outcomes, for rates of natural delivery and weight and length of newborns.

CONCLUSIONS

We conclude that scheduling FET with HRT on weekdays and avoiding work overload at weekends prove efficient and safe in cycle outcome terms. Another reason for the convenience of an HRT protocol is having fewer visits to the clinic compared to natural cycle protocols.

Frozen-thawed blastocyst transfer in natural cycle: feasibility in everyday clinical practice

PURPOSE

Transfer of frozen-thawed embryos in natural cycle is gaining consensus but evidence on this approach is scanty. The aim of this study is reporting on the feasibility of this type of policy in everyday clinical practice.

METHODS

We retrospectively selected all women undergoing the procedure between July 2013 and December 2014. During the study period, women were systematically scheduled for natural cycle if they referred regular menstrual cycles. Hormone replacement therapy (HRT) was conversely prescribed if the woman had irregular menstrual cycles or if the monitoring of the natural cycle failed. The analysis exclusively focussed on the first cycle per woman.

RESULTS

Overall, 251 women were selected. HRT was initially chosen in 52 women, leaving 199 women suitable for the natural cycle. This procedure could be performed in 194 of these women (97%, 95% CI 95-99%). Two additional women initially allocated to HRT ultimately performed the blastocyst transfer with natural cycle. Overall, 196 were thus treated with natural cycle (78%, 95% CI 73-83%). The basal characteristics of the women who did and did not undergo natural cycles were similar with the exceptions of serum FSH (p < 0.001) and AMH (p = 0.03). The live birth rate did not also differ (34% versus 31%, p = 0.63). Characteristics of women treated with the natural cycle who did (n = 67) and did not (n = 129) achieve a live birth did not differ.

CONCLUSION

Frozen-thawed blastocyst transfer in natural cycle can be successfully performed in the vast majority of women.

Modified natural cycle for embryo transfer using frozen-thawed blastocysts: A satisfactory option

OBJECTIVE

To describe pregnancy outcomes of frozen-thawed blastocysts cycles using modified natural cycle frozen embryo transfers (NC-FET) and down-regulated hormonally controlled frozen embryo transfers (HC-FET) protocols.

STUDY DESIGN

This retrospective cohort study included all patients undergoing either modified NC-FET or down-regulated HC-FET using frozen-thawed day 5 embryos. Cycles with donor blastocysts were excluded. Four hundred twenty eight patients underwent a total of 493 FET cycles. Patients with regular menses and evidence of ovulation underwent modified NC-FET. These patients were given hCG 10,000 IU IM on the day of LH-surge. Vaginal progesterone (P4) was started two days later and blastocyst transfer was planned seven days after detecting the LH surge. Anovulatory patients and some ovulatory patients underwent down-regulated HC-FET. These patients were placed on medroxy-progesterone acetate (10mg) for 10days to bring on menses and were also given a half-dose of GnRH-agonist (GnRH-a) on the third day of medroxy-progesterone acetate. Exogenous estradiol was initiated on the third day of menses. Once serum E2 levels reached >500pg/mL and endometrial lining reached >8mm, intramuscular (IM) P4 in oil was administered. Blastocyst FET was planned 6days after initiating P4. The primary outcomes included clinical pregnancy and delivery rates.

RESULTS

There were 197 patients in the modified NC-FET protocol and 181 in the down-regulated HC-FET protocol. Mean age (years), day-3 FSH levels (mIU/mL) and percentage of patients with male factor infertility were significantly higher and mean BMI (kg/m²) was significantly lower in modified NC-FET compared to HC-FET, respectively. Analysis of the first cycle pregnancy outcomes revealed no significant differences in clinical pregnancy rate (54.3% vs. 52.5%) and delivery rate (47.2% vs. 43.6%) between modified NC-FET and HC-FET. Logistic regression analysis showed age (OR=0.939, 95% CI 0.894-0.989, p=0.011), number of blastocysts transferred (OR=1.414, 95% CI 1.046-1.909, p=0.024), and the year of FET (OR=1.127, 95% CI 1.029-1.234, p=0.010) were significant factors impacting clinical pregnancy. An age analysis within three age groups (≤35, 36-39, ≥40) was performed, but no significant difference in clinical pregnancy was observed.

CONCLUSION

Our data suggests that modified NC-FET protocol has comparable pregnancy outcomes to down-regulated HC-FET when utilizing frozen-thawed day 5 embryos.