Frozen versus fresh single blastocyst transfer in ovulatory women: a multicentre, randomised controlled trial

Endometrial thickness is associated with low birthweight in frozen embryo transfer cycles: A retrospective cohort study of 8,235 singleton newborns

OBJECTIVE

To explore the association between endometrial thickness (EMT) and adverse neonatal outcomes in frozen in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) cycles.

METHODS

This retrospective study involved a total of 8,235 women under the age of 35 years who underwent IVF/ICSI cycles and received frozen embryo transfer (FET) at a tertiary-care academic medical from January 2015 to December 2019, resulting in a live singleton newborn. Patients were categorized into three groups depending on EMT: ≤7.5 mm, 7.5-12 mm and >12 mm. The primary outcome was low birthweight (LBW). The secondary outcomes were preterm birth (PTB), small-for-gestational age (SGA), large-for-gestational age (LGA) and high birthweight (HBW).

RESULTS

Compared with EMT >7.5-12 mm group, the risk of being born LBW was statistically significantly increased in the EMT ≤7.5 mm group (adjusted odds ratio [aOR] 2.179; 95% confidence interval [CI], 1.305-3.640; P=.003), while dramatically decreased in the EMT >12 mm group (aOR 0.584; 95% CI, 0.403-0.844; P=.004). Moreover, newborn gender and pregnancy complications were all independent predictors for LBW. Furthermore, a significant decrease in birthweight was found in the EMT ≤7.5 mm group as compared with EMT >7.5-12 mm group and EMT >12 mm group (3,239 ± 612 vs. 3,357 ± 512 and 3,374 ± 479 g, respectively), and similar result was found in term of gestational age (38.41 ± 2.19 vs. 39.01 ± 1.68 and 39.09 ± 1.5 weeks, respectively).

CONCLUSIONS

After frozen IVF/ICSI-ET, EMT ≤7.5 mm is independently associated with increased risk of LBW among women with singleton newborns. Therefore, we suggest that women with EMT ≤7.5 mm after achieving pregnancy by IVF/ICSI-ET treatment should warrant more attention to reduce the risk of delivering a LBW newborn.

Is a freeze-all strategy necessary for all embryo transfers : Fresh embryo transfer without progesterone elevation results in an equivalent pregnancy rate to cryopreserved embryo transfer

Objectives : It has been suggested that the clinical outcomes of frozen-thawed embryo transfer (ET) are superior to those of fresh embryo transfer. We examined whether a freeze-all strategy is necessary for all embryo transfers, and, if not, to evaluate the conditions in which the pregnancy rates of fresh embryo transfer and frozen-thawed ET did not differ. Methods : Patients who underwent blastocyst transfer at Tokushima University Hospital between 2008 and 2019 were enrolled. The clinical outcomes and clinical characteristics of 1,022 patients that underwent fresh embryo transfer and 1,728 patients that underwent frozen-thawed ET were examined retrospectively. We considered the factors that influenced the pregnancy outcomes of fresh embryo transfer. Results : The frozen-thawed ET group exhibited significantly higher pregnancy, live-birth, and miscarriage rates than the fresh embryo transfer group. In the fresh embryo transfer group, a high progesterone level on the day of the human chorionic gonadotropin (hCG) trigger and lower grade embryos were risk factors for a low pregnancy rate. However, in the cases in which the progesterone level was < 1.0 ng / mL the pregnancy rate was equal to that of frozen-thawed ET. Conclusions : A freeze-all strategy is not necessary for embryo transfers, but should be employed in cases involving pre-ovulatory progesterone elevation. J. Med. Invest. 69 : 224-229, August, 2022.

Non-Assisted Hatching Trophectoderm Biopsy Does Not Increase The Risks of Most Adverse Maternal and Neonatal Outcome and May Be More Practical for Busy Clinics: Evidence From China

OBJECTIVE

This study was conducted in order to investigate whether non-assisted hatching trophectoderm (TE) biopsy increases the risks of adverse perinatal outcomes in livebirths following elective single cryopreserved-thawed blastocyst transfer.

PATIENTS AND METHODS

A total of 5,412 cycles from 4,908 women who achieved singleton livebirths between 2013 and 2019 were included in this retrospective cohort study. All embryos in this study were fertilized by intracytoplasmic sperm injection (ICSI) and cryopreserved through vitrification. The main intervention is to open the zona pellucida (ZP) of day 5/6 blastocyst immediately for biopsy without pre-assisted hatching. The main outcome measures are the common maternal and neonatal outcomes, including hypertensive disorders of pregnancy (HDPs), gestational diabetes mellitus (GDM), abnormal placentation, abnormalities in umbilical cord and amniotic fluid, preterm birth, cesarean section, low birth weight, postpartum hemorrhage, and prolonged hospital stay (both mothers and infants). The generalized estimation equation (GEE) was used to control the effects of repeated measurements. The non-conditional logistic regression model was used to examine the associations between embryo biopsy status and each adverse perinatal event. Given that the selection bias and changes in learning curve might affect the results, we selected 1,086 similar (matching tolerance = 0.01) cycles from the ICSI group via propensity score matching (PSM) for second comparisons and adjustment (conditional logistic regression).

RESULTS

After adjusting for confounders, we confirmed that the non-assisted hatching protocol did not increase the risks of most adverse maternal and neonatal outcomes. Despite this, there were increased risks of GDM (aOR: 1.522, 95% CI: 1.141-2.031) and umbilical cord abnormalities (aOR: 11.539, 95% CI: 1.199-111.067) in the biopsy group. In the second comparisons after PSM, GDM incidence in the biopsy group was still higher (7.26% vs. 5.16%, P = 0.042), yet all measurement outcomes were equally likely to occur in both groups after the second adjustment.

CONCLUSIONS

The non-assisted hatching TE biopsy does not increase the risks of most adverse perinatal outcomes. However, there is a higher GDM incidence in the biopsy group, and this association warrants further study. Considering its safety and simplicity, the non-assisted hatching protocol has the potential to become the preferred option for TE biopsy, especially in busy clinics and IVF laboratories.

Early Spontaneous Abortion in Fresh- and Frozen-Embryo Transfers: An Analysis of Over 35,000 Transfer Cycles

BACKGROUND

The aim of this study was to explore the risk factors for early spontaneous abortion (ESA) in fresh- and frozen-embryo transfers.

METHODS

This retrospective cohort study comprised a total of 35,076 patients, including 15,557 women in the fresh-embryo transfer group and 19,519 women in the frozen-embryo transfer group from January 2016 to December 2020. The primary outcome of this study was ESA, which we defined as the termination of embryonic development before 12 weeks of pregnancy (i.e., an early abortion after artificial multi-fetal pregnancy reduction was excluded).

RESULTS

In the 35,076 ART transfer cycles, the incidence of ESA was 5.77% (2023/35,076), and the incidence rates for ESA in fresh and frozen cycles were 4.93% (767 of 15,557) and 6.43% (1,256 of 19,519), respectively. Using a multivariate logistic regression analysis model, maternal age, body mass index (BMI), and number of embryos transferred were independent predictors for ESA. In addition, frozen-thawed transfer was a risk factor for ESA as compared with fresh transfer (OR = 1.207; 95% CI, 1.094-1.331; P = 0.000), blastocyst transfer was risk factor for ESA as compared with cleavage transfer (OR =1.373; 95% CI, 1.186-1.591; P = 0.000 in the total group; OR = 1.291; 95% CI, 1.111-1.499; P = 0.001 in the frozen-transfer group), and unexplained infertility was a protective factor for ESA only in the frozen group (OR = 0.746; 95% CI, 0.565-0.984; P = 0.038).

CONCLUSIONS

Maternal age, BMI, number of embryos transferred, and frozen-thawed transfer were independent risk factors for ESA in assisted reproductive technology treatment cycles.

Higher blastocyst implantation in frozen versus fresh embryo transfers in good prognosis patients

BACKGROUND

There is emerging evidence that frozen embryo transfers provide a more favorable environment for implantation as compared to fresh embryo transfers. Our objective was to determine if there is a clinical benefit to frozen versus fresh blastocyst transfers in good prognosis patients.

METHODS

Subjects undergoing their first or second IVF/ICSI cycle <38 years of age in an OCP pretreated GnRH antagonist stimulation protocol with supernumerary embryos available for blastocyst cryopreservation were eligible for analysis. Primary transfer was exclusively blastocyst transfer. Exclusion criteria consisted of rescue ICSI, preimplantation genetic testing, donor oocytes, and surrogacy. The cohort was divided into two groups based on whether they underwent a fresh vs. frozen primary transfer. The implantation rates were compared using mixed-effects logistic regression. The clinical pregnancy and live birth rates were compared using logistic regression adjusted for number of oocytes retrieved and number of embryos transferred. All models included age, reason for treatment, and number of prior births as covariates.

RESULTS

A total of 615 subjects were included in the study. There were no differences in the two groups with respect to age, BMI, baseline ovarian reserve testing, total gonadotropin dosage, and duration of stimulation. The implantation rate was higher in the frozen-embryo group as compared to the fresh-embryo group (59% and 48% respectively; OR 1.58; 95% CI 1.02-2.44). There was a trend towards higher clinical pregnancy and live birth rates in the frozen-embryo group. These differences persisted in the adjusted analysis.

CONCLUSIONS

Among good prognosis patients undergoing IVF, frozen embryo transfer was associated with improved implantation rates. Consideration should be given to primary frozen blastocyst transfer in this population.

The vitrification system may affect preterm and cesarean delivery rates after single vitrified blastocyst transfer

The purpose of this study was to investigate the possible effects of different vitrification systems on single vitrified blastocyst transfer cycles. The clinical and birth outcomes of 412 patients who underwent single vitrified blastocyst transfer between January 2018 and June 2020 were retrospectively analyzed and compared between patients who underwent blastocyst vitrification with kit A (group A, 196 patients) and those who underwent blastocyst vitrification with kit B (group B, 216 patients). Clinical outcomes, including the clinical pregnancy rate, ongoing pregnancy rate, early miscarriage rate, late miscarriage rate, ectopic pregnancy rate, twin pregnancy rate, and induced labor rate due to fetal malformation, were not significantly different between the two groups (P > 0.05). The preterm delivery rate among singleton newborns (11.57% vs. 3.23%, P < 0.05) and the cesarean delivery rate were significantly higher in group B than in group A (70.25% vs. 57.26%, P < 0.05). Birth outcomes, including the male-to-female ratio, low-birth-weight rate, macrosomia rate, birth defect rate, newborn gestational age, neonatal body weight, and singleton neonatal body length, were not significantly different (P > 0.05). Our findings suggest that different vitrification systems might differentially affect birth outcomes. Such disparity could reflect differences in kit composition and/or protocol.ABBREVIATIONS: DMSO: dimethyl sulfoxide; ES: equilibration solution; VS: vitrification solution; BMI: body mass index; ICSI: intracytoplasmic sperm injection; OR: odds ratio; CI: confidence interval.

Does the freeze-all strategy improve the cumulative live birth rate and the time to become pregnant in IVF cycles?

PURPOSE

The freeze-all strategy is widely used for ovarian hyperstimulation syndrome (OHSS) prevention. Indeed, it increases live birth rates among high responders and prevents preterm birth and small for gestational age. Why should not we extend it to all?

METHODS

A retrospective and monocentric study was conducted between January 2008 and January 2018 comparing the cumulative live birth rates (CLBR) between patients having undergone FAS and a control group using fresh embryo transfer (FET) and having at least one frozen embryo available. Analyses were made for the entire cohort (population 1) and for different subgroups according to confounding factors selected by a logistic regression (population 3), and to the BELRAP (Belgian Register for Assisted Procreation) criteria (population 2).

RESULTS

2216 patients were divided into two groups: Freeze all (FA), 233 patients and control (C), 1983 patients. The CLBR was 50.2% vs 58.1% P = 0.021 for population 1 and 53.2% vs 63.3% P = 0.023 for population 2, including 124 cases and 1241 controls. The CLBR stayed in favour of the C group: 70.1% vs 55.9% P = 0.03 even when confounding variables were excluded (FA and C group, respectively, 109 and 770 patients). The median time to become pregnant was equally in favour of the C group with a median of 5 days against 61 days.

CONCLUSION

CLBR is significantly lower in the FA group compared to the C group with a longer time to become pregnant. Nevertheless, the CLBR in the FA group remains superior to that observed in previous studies.

Novel nucleic acid aptamer gold (Au)-nanoparticles (AuNPs-AptHLA-G5-1 and AuNPs-AptHLA-G5-2) to detect the soluble human leukocyte antigen G5 subtype (HLA-G5) in liquid samples

Background

The human leukocyte antigen G5 subtype (HLA-G5) is a major histocompatibility complex (MHC) molecule that is selectively expressed at the maternal-foetal tissue interface and is required for the successful implantation of the in vitro fertilized embryo. It is critical to detect HLA-G5, especially HLA-G5 expression in embryo fluid, during in vitro embryo incubation and culture. However, the specificity and sensitivity of traditional ELISA methods to detect sHLA-G5 are insufficient. This work aimed to explore novel nucleic acid aptamer gold (Au)-nanoparticles to detect soluble HLA-G5 in liquid samples.

Methods

Soluble HLA-G5 was obtained using a prokaryotic expression system, and two novel aptamers (HLA-G5-Apt1 and HLA-G5-Apt2) detecting HLA-G5 were screened by the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) method. Small (10 nm) gold nanoparticles (AuNPs) were incubated with AptHLAs to form two novel nucleic acid aptamers: Au-nanoparticles (AuNPs-AptHLA-G5-1 and AuNPs-AptHLA-G5-2).

Results

The results showed that AptHLA-G5-1 and AptHLA-G5-2 have a high affinity for HLA-G5 and can detect its presence in liquid samples. Using the colorimetric sensing method, AuNPs-AptHLA-G1 had a detection limit as low as 20 ng/mL (recovery range between 98.7% to 102.0%), while AuNPs-AptHLA-G2 had a detection limit as low as 20 ng/mL (recovery range between 98.9% to 103.6%).

Conclusions

Our work demonstrates that novel AuNPs are efficient detectors for HLA-G5 and are useful for diagnosis and treatment in the field of obstetrics-gynaecology.

Corpus luteum number and the maternal renin-angiotensin-aldosterone system as determinants of utero-placental (vascular) development: the Rotterdam Periconceptional Cohort

BACKGROUND

Pregnancies with > 1 corpus luteum (CL) display a hyperdynamic circulation and an increased risk of small-for-gestational age deliveries. Among the factors released by the CL is prorenin, the inactive precursor of renin. Since the renin-angiotensin-aldosterone system (RAAS) is involved in early hemodynamic pregnancy adaptation, we linked both CL number and first-trimester concentrations of prorenin (as an indicator of RAAS activity) and the aldosterone/renin ratio (as an indicator of angiotensin-independent aldosterone effectiveness) to non-invasive markers of utero-placental (vascular) development, measured longitudinally from the first trimester onwards.

METHODS

A total of 201 women, who conceived naturally or after in-vitro fertilization treatment (with 0 (n = 8), 1 (n = 143), or > 1 (n = 51) CL), were selected from the Rotterdam Periconceptional Cohort. Maternal RAAS components were determined at 11 weeks gestation. Placental volume and utero-placental vascular volume were measured from transvaginal 3D ultrasound scans at 7, 9 and 11 weeks gestation, pulsatility and resistance indices of the uterine arteries were assessed by pulsed wave Doppler ultrasounds at 7, 9, 11, 13, 22 and 32 weeks gestation. At birth placental weight was obtained using standardized procedures.

RESULTS

Pregnancies without a CL show lower uterine artery indices throughout gestation than 1 CL and > 1 CL pregnancies, while parameters of placental development are comparable among the CL groups. After adjustment for patient- and treatment-related factors, first-trimester prorenin concentrations are positively associated with uterine artery pulsatility and resistance indices (β 0.06, 95% CI 0.01;0.12, p = 0.04 and β 0.10, 95% CI 0.01;0.20, p = 0.04, respectively), while high prorenin concentrations are negatively associated with first-trimester utero-placental vascular volume (β -0.23, 95% CI -0.44;-0.02, p = 0.04) and placental weight (β -93.8, 95%CI -160.3;-27.4, p = 0.006). In contrast, the aldosterone/renin ratio is positively associated with first-trimester placental volume (β 0.12, 95% CI 0.01;0.24, p = 0.04).

CONCLUSIONS

The absence of a CL, resulting in low prorenin concentrations, associates with low uterine artery pulsatility and resistance, while high prorenin concentrations associate with a low utero-placental vascular volume and weight. These data support a scenario in which excess prorenin, by upregulating angiotensin II, increases uterine resistance, thereby preventing normal placental (vascular) development, and increasing the risk of small-for-gestational age deliveries. Simultaneously, high aldosterone concentrations, by ensuring volume expansion, exert the opposite.

TOB1 modulates the decidualization of human endometrial stromal cells via the Notch pathway

BACKGROUND

Decidualization is critical for embryo implantation and the success of pregnancy; however, the mechanisms underlying this process remain largely unknown.

MATERIALS AND METHODS

In the present study, RNA sequencing was used to detect the expression levels of transducer of ERBB2/1(TOB1) in endometrial samples derived from proliferative and secretory phases. A decidualization model was induced using the combination of estrogen (E2) and progestin (P4) in human endometrial stromal cells (HESCs). The cell counting kit-8 assay was used to detect the viability of HESCs. Related proteins were detected by qPCR and western blot.

RESULT

The results indicated that TOB1 expression was upregulated in the secretory endometrial samples compared with the corresponding expression observed in the proliferative samples. The expression levels of TOB1 and Notch1 were markedly increased in E2P4-treated HESCs compared with those in the control cells. Treatment with E2P4 strongly suppressed the proliferation of HESCs and induced a G₁-phase cell cycle arrest. These effects were abolished by knockdown of TOB1 or treatment with of the cells with the Notch inhibitor N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butyl ester.

CONCLUSIONS

Therefore, these findings highlighted an important role for TOB1/Notch signaling in E2P4-induced decidualization in HESCs, which may provide novel targets for improving the endometrial receptivity.

Assessing couples' preferences for fresh or frozen embryo transfer: a discrete choice experiment

STUDY QUESTION

What are couples' preferences for fresh embryo transfer versus freezing of all embryos followed by frozen embryo transfer and the associated clinical outcomes that may differentiate them?

SUMMARY ANSWER

Couples' preferences are driven by anticipated chances of live birth, miscarriage, neonatal complications, and costs but not by the differences in the treatment process (including delay of embryo transfer linked to frozen embryo transfer and risk of ovarian hyperstimulation syndrome (OHSS) associated with fresh embryo transfer).

WHAT IS KNOWN ALREADY

A policy of freezing all embryos followed by transfer of frozen embryos results in livebirth rates which are similar to or higher than those following the transfer of fresh embryos while reducing the risk of OHSS and small for gestational age babies: it can, however, increase the risk of pre-eclampsia and large for gestational age offspring. Hence, the controversy continues over whether to do fresh embryo transfer or freeze all embryos followed by frozen embryo transfer.

STUDY DESIGN, SIZE, DURATION

We used a discrete choice experiment (DCE) technique to survey infertile couples between August 2018 and January 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We asked IVF naïve couples attending a tertiary referral centre to independently complete a questionnaire with nine hypothetical choice tasks between fresh and frozen embryo transfer. The alternatives varied across the choice occurrences on several attributes including efficacy (live birth rate), safety (miscarriage rate, neonatal complication rate), and cost of treatment. We assumed that a freeze-all strategy prolonged treatment but reduced the risk of OHSS. An error components mixed logit model was used to estimate the relative value (utility) that couples placed on the alternative treatment approaches and the attributes used to describe them. Willingness to pay and marginal rates of substitution between the non-cost attributes were calculated. A total of 360 individual questionnaires were given to 180 couples who fulfilled the inclusion criteria, of which 212 were completed and returned Our study population included 3 same sex couples (2 females and 1 male) and 101 heterosexual couples. Four questionnaires were filled by one partner only. The response rate was 58.8%.

MAIN RESULTS AND THE ROLE OF CHANCE

Couples preferred both fresh and frozen embryo transfer (odds ratio 27.93 and 28.06, respectively) compared with no IVF treatment, with no strong preference for fresh over frozen. Couples strongly preferred any IVF technique that offered an increase in live birth rates by 5% (P = 0.006) and 15% (P < 0.0001), reduced miscarriage by 18% (P < 0.0001) and diminished neonatal complications by 10% (P < 0.0001). Respondents were willing to pay an additional £2451 (95% CI 604 - 4299) and £761 (95% CI 5056-9265) for a 5 and 15% increase in the chance of live birth, respectively, regardless of whether this involved fresh or frozen embryos. They required compensation of £5230 (95% CI 3320 - 7141) and £13 245 (95% CI 10 110-16 380) to accept a 10 and 25% increase in the risk of neonatal complications, respectively (P < 0.001). Results indicated that couples would be willing to accept a 1.26% (95% CI 1.001 - 1.706) reduction in the live birth rate for a 1% reduction in the risk of neonatal complications per live birth. Older couples appeared to place less emphasis on the risk of neonatal complications than younger couples.

LIMITATIONS, REASONS FOR CAUTION

DCEs can elicit intentions which may not reflect actual behaviour. The external validity of this study is limited by the fact that it was conducted in a single centre with generous public funding for IVF. We cannot rule out the potential for selection or responder bias.

WIDER IMPLICATIONS OF THE FINDINGS

If a strategy of freeze all was to be implemented it would appear to be acceptable to patients, if either success rates can be improved or neonatal complications reduced. Live birth rates, neonatal complication rates, miscarriage rates, and cost are more likely to drive their preferences than a slight delay in the treatment process. The results of this study have important implications for future economic evaluations of IVF, as they suggest that the appropriate balance needs to be struck between success and safety. A holistic approach incorporating patient preferences for expected clinical outcomes and risks should be taken into consideration for individualized care.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was sought for this study. A.M. is the chief investigator of the randomized controlled trial 'Freeze all'. S.B. is an Editor in Chief of Human Reproduction Open. The other co-authors have no conflicts of interest to declare. Graham Scotland reports non-financial support from Merck KGaA, Darmstadt, Germany, outside the submitted work.

TRIAL REGISTRATION NUMBER

N/A.

The Effects of Different Post-thawed Culture Periods on Clinical Outcomes in Frozen Embryo Transfer Cycle

The purpose of this study is to evaluate the effects of different post-thawed culture periods on the clinical outcomes. 9381 frozen embryo transfer (FET) cycles were divided into three groups according to female age: < 35, 35-39, and > 39 years, and two groups depending on post-thawed culture period before transfer: short culture (2-3 h) group (S) and long culture (18-20 h) group (L). According to the increment number of post-thawed embryos, the L group divided into three groups: ≤ 2, one ≤ 2 and the other > 2, and > 2 groups. Pregnancy outcomes included the implantation rate (IR), clinical pregnancy rate (CPR), multiple pregnancy rate (MPR), live birth rate (LBR), and neonatal characteristics. Long post-thawed culture caused a significant increase in the IR, CPR, MPR, and LBR (p = 0.000, 0.004, 0.037, and 0.001; CI = 1.06-1.194, 1.042-1.237, 1.008-1.254, and 1.054-1.245, respectively), and blastomere increment number also had a significant effect on IR, CPR, MPR, and LBR (p = 0.000, 0.000, 0.000, and 0.000, respectively). No significant differences were present in neonatal characteristics between the two post-thawed culture groups. Singleton group had a higher average gestational age and birthweight as well as a lower cesarean section rate, preterm labor rate, and low birthweight rate than twins group. Long post-thawed culture was associated with higher IR, CPR, MPR, and LBR, and transferring a well-developed embryo after long post-thawed culture might be a viable embryo transfer strategy to decrease MPR while maintaining CPR and LBR.

A Novel Promising Endometrial Preparation Protocol for Frozen-Thawed Embryo Transfer: A Randomized Controlled Trial

Background

In recent years frozen-thawed embryo transfer (FET) has played an increasingly important role in ART, but there is limited consensus on the most effective method of endometrial preparation (EP) for FET. Inspired by significantly higher implantation rate and clinical pregnancy rate of the depot GnRH-a protocol, we proposed a novel EP protocol named down-regulation ovulation-induction (DROI) aimed to improve pregnancy outcomes of FET.

Methods

This was a single-center, randomized controlled pilot trial. A total of 307 patients with freeze-all strategy scheduled for first FET were enrolled in the study. A total 261 embryos were transferred in DROI-FET group including 156 patients and 266 embryos were transferred in mNC-FET group including 151 patients. Reproductive outcomes were compared between the two groups.

Results

The basic characteristics of patients, and the average number, quality and stage of embryos transferred were comparable between the two groups. Our primary outcome, implantation rate(IR) in DROI-FET group, was significantly higher than that of the mNC-FET group (54.41% versus 35.71%, P<0.01). The clinical pregnancy rate (CPR) and ongoing pregnancy rate (OPR) in DROI-FET group was also higher than that in mNC-FET group (69.87% versus 50.33%, P<0.01; 64.10% versus 42.38%, P<0.01).

Conclusions

Compared to existing endometrial preparation methods, the DROI protocol might be the more efficient and promising protocol.

The evolving landscape of donor egg treatment: success, women's choice, and anonymity

PURPOSE

To analyze donor oocyte (DE) data across 6 years for oocyte usage efficiency, trends, and whether changes impacted outcomes.

METHODS

From 2014 to 2019, 323 DE embryo transfers were completed in 200 recipients using oocytes derived of 163 donors. We assessed data for oocytes being freshly retrieved (FRESH-EGG) vs. purchased frozen (FROZEN-EGG); embryos transferred fresh (FRESH-ET) vs. frozen (FROZEN-ET); cycles SHARED (two recipients) vs. SOLE (one recipient); single (SET) vs. double (DET) embryo transfers and usage of PGT-A. Primary outcome was ongoing pregnancy plus live birth (OP/LB) rate.

RESULTS

A total of 229 FRESH-EGG (70%) and 94 FROZEN-EGG (30%) cycles were completed. Overall, the use of FRESH-EGG yielded a higher OP/LB compared to FROZEN-EGG (49% vs. 30%, p = 0.001); within the FRESH-EGG group, OP/LB was similar when comparing FRESH-ET vs. FROZEN-ET (58% vs. 45%, p = 0.07). Within the FRESH-ET group, those using FRESH-EGG had a higher OP/LB than those using FROZEN-EGG (58% vs. 27%, p < 0.001). SHARED vs. SOLE cycles (p = 0.6), donor age (21-32 years; p = 0.4), and age of intended parents (maternal p = 0.3, paternal p = 0.2) did not significantly impact OP/LB. Notably, the use of PGT-A did not improve odds for an OP/LB (p = 0.7).

CONCLUSION

The use of FRESH-EGG with FRESH-ET without PGT-A remains superior to newer DE treatment combinations. Specifically, the use of FROZEN-EGG and PGT-A did not improve outcomes. Although changing DE practices may enhance experience and affordability, patients and providers must appreciate that choices do not always favorably impact success. Additionally, newly available genetic-ancestry testing may pose longer-term ramifications mandating change in treatment and/or counseling.

Ovarian stimulation reduces fetal growth by dysregulating uterine natural killer cells in mice

Ovarian stimulation is associated with a higher risk of low birth weight. However, the precise mechanisms by which ovarian stimulation increases the chances of low birth weight remain unclear. In this mouse model study, in vivo developed blastocysts that were not exposed to gonadotropins were transferred into pseudopregnant females that had mated naturally (the control group), pseudopregnant females that had been administered a low dose of ovulation-stimulating hormone (the L-SO group) and pseudopregnant females that had been administered a high dose of ovulation-stimulating hormone (the H-SO group). The embryo implantation rate and fetal weight were significantly lower in the L-SO and H-SO groups than in the control group. The density of Dolichos biflorus agglutinin (DBA)⁺ uterine natural killer (uNK) cells in the decidua basalis was significantly lower in the L-SO and H-SO groups than in the control group. Ovarian stimulation also downregulated a variety of cytokines related to uNK cells that are involved in placental angiogenesis and trophoblast invasion. Collectively, our findings indicate that ovarian stimulation impairs DBA⁺ uNK cell density in the decidua basalis, which may downregulate uNK-related cytokine secretion and influence placental angiogenesis and restrict fetal growth in mice.

Advanced trophectoderm quality increases the risk of a large for gestational age baby in single frozen-thawed blastocyst transfer cycles

STUDY QUESTION

Does trophectoderm (TE) quality affect birthweight after single frozen-thawed blastocyst transfer?

SUMMARY ANSWER

Transfer of single blastocyst with advanced TE quality was associated with higher birthweight and increased risk of a large for gestational age (LGA) baby.

WHAT IS KNOWN ALREADY

Transfer of blastocysts with advanced TE quality results in higher ongoing pregnancy rates and a lower miscarriage risk. However, data on the relationship between TE quality and birthweight are still lacking.

STUDY DESIGN, SIZE, DURATION

This retrospective cohort study at a tertiary-care academic medical center included 1548 singleton babies born from single frozen-thawed blastocyst transfer from January 2011 to June 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Babies were grouped into four groups according to embryo expansion (Stages 3, 4, 5 and 6), three groups according to inner cell mass (ICM) quality (A, B and C), and three groups according to TE quality (A, B and C). Main outcomes included absolute birthweight, Z-scores adjusted for gestational age and gender, and adverse neonatal outcomes. Multivariable linear and logistic regression analyses were performed to investigate the association of neonatal outcomes with expansion stage, ICM quality and TE quality.

MAIN RESULTS AND THE ROLE OF CHANCE

As TE quality decreased, birthweight (3468.10 ± 471.52, 3357.69 ± 522.06, and 3288.79 ± 501.90 for A, B and C, respectively, P = 0.002), Z-scores (0.59 ± 1.07, 0.42 ± 1.04, and 0.27 ± 1.06 for A, B and C, respectively, P = 0.002) and incidence of LGA (28.9%, 19.7% and 17.4% for A, B and C, respectively, P = 0.027) decreased correspondingly. After adjusting for confounders, compared with the Grade A group, blastocysts with TE Grade B (standardized coefficients (β): -127.97 g, 95% CI: -234.46 to -21.47, P = 0.019) and blastocysts with TE grade C (β: -200.27 g, 95% CI: -320.69 to -79.86, P = 0.001) resulted in offspring with lower birthweight. Blastocysts with TE grade C brought babies with lower Z-scores than TE Grade A (β: -0.35, 95% CI: -0.59 to -0.10, P = 0.005). Also, embryos with TE Grade B (adjusted odds ratio (aOR):0.91, 95% CI: 0.84 to 0.99, P = 0.033) and embryos with TE Grade C (aOR : 0.89, 95% CI: 0.81 to 0.98, P = 0.016) had lower chance of leading to a LGA baby than those with TE Grade A. No association between neonatal outcomes with embryo expansion stage and ICM was observed (all P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

The retrospective design, lack of controlling for several unknown confounders, and inter-observer variation limited this study.

WIDER IMPLICATIONS OF THE FINDINGS

The study extends our knowledge of the down-stream effect of TE quality on newborn birthweight and the risk of LGA.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by National Key R&D Program of China (2018YFC1003000), National Natural Science Foundation of China (81771533 to Y.P.K. and 31200825 to L.S.) and Innovative Research Team of High-level Local Universities in Shanghai (SSMU-ZLCX20180401), Shanghai Sailing Program(21YF1423200) and the Fundamental research program funding of Ninth People's Hospital affiliated to Shanghai Jiao Tong university School of Medicine (JYZZ117). The authors declare no conflict of interest in this present study.

TRIAL REGISTRATION NUMBER

N/A.

Maternal and neonatal outcomes following blastocyst biopsy for PGT in single vitrified-warmed embryo transfer cycles

RESEARCH QUESTION

Does blastocyst biopsy for preimplantation genetic testing (PGT) increase the risk of adverse maternal and neonatal outcomes?

STUDY DESIGN

Retrospective cohort study of 5097 single vitrified-warmed blastocyst transfer cycles from January 2016 to December 2018, with 2061 cycles in the biopsied group and 3036 cycles in the unbiopsied group enrolled in the analyses. Maternal and neonatal outcomes were compared between the two groups.

RESULTS

The live birth rate in the biopsied group (41.1%) was significantly higher than that in the unbiopsied group (35.6%, adjusted odds ratio [aOR] 1.27, 95% confidence interval [CI] 1.05-1.54, P = 0.012) after adjusting for maternal age, maternal body mass index, gravidity, parity, infertility diagnosis, timing of blastocyst transfer, blastocyst quality, regimen of endometrial preparation, endometrial thickness before transfer and treatment year. The rates of total pregnancy loss (25.4% versus 32.2%, aOR 0.69, 95% CI 0.52-0.91, P = 0.008) and early miscarriage (12.1% versus 17.3%, aOR 0.56, 95% CI 0.38-0.83, P = 0.004) were significantly lower in the biopsied group than in the unbiopsied group. No significant differences were found in sex ratio or the risks of hypertensive disorders in pregnancy, diabetes in pregnancy, placenta previa, preterm premature rupture of membranes, low birthweight, very low birthweight, macrosomia, small for gestational age, large for gestational age or birth defects between the two groups. When the subgroup analyses were conducted based on different types of PGT, similar patterns were found for all types.

CONCLUSION

Blastocyst biopsy might not increase the risks of adverse maternal and neonatal outcomes in the short term.

Preimplantation genetic testing is not a preferred recommendation for patients with X chromosome abnormalities

STUDY QUESTION

Should women with X chromosome abnormalities (XCAs) be recommended to have embryos selected by both morphological and cytogenetic assessment through preimplantation genetic testing (PGT) rather than morphological assessment only in conventional IVF/ICSI treatment?

SUMMARY ANSWER

PGT is not a preferred recommendation for women with XCAs in the absence of other PGT indications.

WHAT IS KNOWN ALREADY

XCAs are the most frequent sort of chromosomal aberrations in infertile women. Patients with a complete or partial absence of one X chromosome, diagnosed as Turner Syndrome (TS), demonstrate low spontaneous pregnancy rates (5-7%) and high miscarriage rates (22.8-30.8%), as well as high chances of birth defects (20%). PGT is known to improve pregnancy rates and decrease the incidence of miscarriage in couples with chromosomal aberrations such as Robertsonian and reciprocal translocations and Klinefelter Syndrome.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study was conducted with 394 women with XCAs and undergoing their first oocyte retrieval and first embryo transfer cycle from June 2011 to August 2019 in the Reproductive Hospital Affiliated to Shandong University.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pregnancy outcomes were compared between the conventional IVF/ICSI group (n = 284) and the PGT group (n = 110) in the first fresh or frozen embryo transfer cycle for each woman with XCAs. Three platforms were applied in PGT: fluorescence in situ hybridisation (FISH, n = 34), array comparative genomic hybridisation (aCGH, n = 24) and next-generation sequencing (NGS, n = 51). The embryo aneuploidy rate and distribution of embryonic chromosomal aberrations revealed by aCGH or NGS were analysed and stratified by maternal age and type of XCAs to assess the effect of maternal XCAs on embryo karyotypes.

MAIN RESULT AND THE ROLE OF CHANCE

The live birth rate (LBR) per embryo transfer was similar between the PGT group and IVF/ICSI group both in the first cycle of fresh or frozen embryo transfer respectively (39.13% in PGTFISH vs 42.58% in IVF/ICSI, Padj=0.558; 66.67% in PGTFISH vs 52.08% in PGTaCGH/NGS vs 53.06% in IVF/ICSI, Padj=0.756), as was the clinical pregnancy rate (60.87% in PGTFISH vs 50.97% in IVF/ICSI, Padj =0.672; 88.89% in PGTFISH vs 58.33% in PGTaCGH/NGS vs 69.39% in IVF/ICSI, Padj =0.480) and the pregnancy loss rate (35.71% in PGTFISH vs 16.46% in IVF/ICSI, Padj =0.136; 12.50% in PGTFISH vs 10.71% in PGTaCGH/NGS vs 23.53% in IVF/ICSI, Padj =0.352). The rates of maternal and neonatal complications were also comparable between the PGT and IVF/ICSI groups with fresh and frozen transfers respectively (10.00% vs 8.85%, P = 1.000; 21.74% vs 14.55%, P = 0.272). Intriguingly, the distribution of embryonic chromosome abnormalities was more frequent on autosomes 22 (20.39%), 21 (18.45%) and 16 (17.47%), compared with the X chromosome (8.73%).

LIMITATIONS, REASONS FOR CAUTION

Selection bias is an inherent drawback of a retrospective study. First, our participants hosted 4.84% X chromosome mosaicism with few typical somatic anomalies of TS. Second, the incidences of history of recurrent miscarriage and abnormal offspring in the PGT group were higher than in IVF/ICSI group although binary logistic regression analysis was performed to attenuate the modifying effect of confounding factors. Third, FISH performed in this study only used X/Y probes and lacked the reference of autosome, which might have resulted in misdiagnosis and bias. Finally, intrinsic disadvantages could not be totally avoided due to the retrospective nature of this study.

WIDER IMPLICATION OF THE FINDINGS

In the current study, comparable pregnancy outcomes were revealed among a large cohort of women with XCAs undergoing their first cycles of PGT or conventional IVF/ICSI treatment. Moreover, the X chromosome abnormality was illustrated to cause no higher frequency of aberrations in embryos. Our data provided perspectives for genetic and reproductive counselling to XCAs individuals and their families.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by National Research and Development Plan (2016YFC1000604 and 2017YFC1001100), the National Natural Science Foundation of China (81701406), Shandong Science Fund for Distinguished Young Scholars (JQ201720), Taishan Scholars Program for Young Experts of Shandong Province (tsqn20161069) and Projects of Medical and Health Technology Development Program in Shandong Province (202005010520, 202005010523 and 2016WS0368). There is no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Clinical and perinatal outcomes of fresh single-blastocyst-transfer cycles under an early follicular phase prolonged protocol according to day of trigger estradiol levels

Backgroud

This study’s objectives were to compare the clinical, perinatal, and obstetrical outcomes of patients with different estradiol (E₂) levels in fresh single-blastocyst-transfer (SBT) cycles under an early follicular phase prolonged regimen on the day of trigger.

Methods

We recruited patients in fresh SBT cycles (n = 771) undergoing early follicular phase prolonged protocols with β-hCG values above 10 IU/L between June 2016 and December 2018. Patients who met the inclusion and exclusion criteria were divided into four groups according to their serum E₂ level percentages on the day of trigger: <25^th, 25^th–50^th, 51^st–75^th, and >75^th percentile groups.

Results

Although the rates of clinical pregnancy (85.57% (166/194)), embryo implantation 86.60% (168/194), ongoing pregnancy (71.13% (138/194)), and live birth (71.13% (138/194)) were lowest in the >75th percentile group, we did not observe any significant differences (all P > 0.05). We used this information to predict the rate of severe ovarian hyperstimulation syndrome (OHSS) area under the curve (AUC) = 72.39%, P = 0.029, cut off value of E₂ = 2,893 pg/ml with the 75% sensitivity and 70% specificity. The 51^st–75^th percentile group had the highest rates of low birth weight infants (11.73% (19/162), P = 0.0408), premature delivery (11.43% (20/175), P = 0.0269), admission to the neonatal intensive care unit (NICU) (10.49% (17/162), P = 0.0029), twin pregnancies (8.57% (15/175), P = 0.0047), and monochorionic diamniotic pregnancies (8.57% (15/175); P = 0.001). We did not observe statistical differences in obstetrics complications, including gestational diabetes mellitus (GDM), gestational hypertension, placenta previa, premature rupture of membranes (PROM), and preterm premature rupture of membranes (PPROM).

Conclusion

We concluded that serum E₂ levels on the day of trigger were not good predictors of live birth rate or perinatal and obstetrical outcomes. However, we found that high E₂ levels may not be conducive to persistent pregnancies. The E₂ level on the day of trigger can still be used to predict the incidence of early onset severe OHSS in the fresh SBT cycle.

The influence of frozen-thawed and fresh embryo transfer on utero-placental (vascular) development: the Rotterdam Periconception cohort

STUDY QUESTION

Does frozen-thawed or fresh embryo transfer (ET) influence utero-placental (vascular) development, when studied using three-dimensional (3D) ultrasound and virtual reality imaging techniques?

SUMMARY ANSWER

In the first trimester, placental developmental parameters, that is, placental volume (PV) and utero-placental vascular volume (uPVV), were comparable between pregnancies resulting from frozen-thawed ET, fresh ET and natural conception; and in the second and the third trimester, uterine artery Doppler indices were lower in pregnancies after frozen-thawed ET compared to pregnancies after fresh ET and natural conception.

WHAT IS KNOWN ALREADY

Pregnancies after frozen-thawed ET are at risk of developing placenta-related pregnancy complications. There is strong evidence that impaired first-trimester spiral artery remodelling is involved in the pathophysiology of these complications. Studies on longitudinal placental development in pregnancies with different modes of conception, that is, after frozen-thawed ET, fresh ET or natural conception, are lacking.

STUDY, DESIGN, SIZE, DURATION

Women with singleton pregnancies were included before 10 weeks of gestation, between January 2017 and July 2018, as a subcohort of the ongoing Rotterdam Periconception cohort. Results were partially validated in 722 women from the total cohort, which was conducted from November 2010 onwards.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 214 women, of whom 32 conceived after frozen-thawed ET, 56 conceived after fresh ET and 126 conceived naturally, were selected. PV and uPVV measurements were obtained at 7, 9 and 11 weeks of gestation by transvaginal 3D (power Doppler) ultrasound. The uterine artery pulsatility index (UtA-PI) and resistance index (UtA-RI) were measured transvaginally at 7, 9, 11 and 13 weeks and abdominally at 22 and 32 weeks of gestation by pulsed wave Doppler ultrasound. In the validation cohort, the PV was measured in 722 women. Associations between mode of conception and placental development were studied using linear mixed models.

MAIN RESULTS AND THE ROLE OF CHANCE

First-trimester parameters of placental development, that is, PV, uPVV, UtA-PI and UtA-RI, were comparable between pregnancies after frozen-thawed and fresh ET and naturally conceived pregnancies. In our validation cohort, comparable results were found for PV. However, the second- and third-trimester UtA-PI and UtA-RI in pregnancies after frozen-thawed ET were significantly lower than in pregnancies after fresh ET (βUtA-PI -0.158 (95% CI: -0.268, -0.048), P = 0.005; βUtA-RI -0.052 (95% CI: -0.089, -0.015), P = 0.006). The second- and third-trimester uterine artery indices in pregnancies after fresh ET were comparable to those in pregnancies after natural conception.

LIMITATIONS, REASONS FOR CAUTION

The main limitation of this study is the lack of power to optimally detect differences in placental development and placenta-related pregnancy outcomes between pregnancies after different modes of conception. Moreover, our population was selected from a tertiary hospital and included a relatively limited number of pregnancies. Therefore, external validity of the results should be confirmed in a larger sample size.

WIDER IMPLICATIONS OF THE FINDINGS

These findings indicate no significant impact of conception mode on early placental development and a beneficial impact for frozen-thawed ET on the second- and third-trimester Doppler indices. This suggests that frozen-thawed ET may not be as detrimental for placental perfusion as previous research has demonstrated. As the number of clinics applying the 'freeze-all strategy' increases, future research should focus on establishing the optimal uterine environment, with regards to hormonal preparation, prior to ET to reduce placental-related pregnancy complications after frozen-thawed ET.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by the Erasmus MC Medical Research Advisor Committee's 'Health Care Efficiency Research' program and the department of Obstetrics and Gynaecology of the Erasmus MC, University Medical Center, Rotterdam, The Netherlands. JSEL reports grants and personal fees from Ferring, personal fees from Titus Healthcare, grants and personal fees from Ansh Labs, grants from NIH, grants from Dutch Heart Association and grants from ZonMW outside the submitted work. None of the other authors have a conflict of interest.

TRIAL REGISTRATION NUMBER

Registered at the Dutch Trial Register (NTR6684).

Time associations between U.S. birth rates and add-Ons to IVF practice between 2005-2016

Until 2010, the National Assisted Reproductive Technology Surveillance System (NASS) report, published annually by the Center for Disease Control and Prevention (CDC), demonstrated almost constantly improving live birth rates following fresh non-donor (fnd) in vitro fertilization (IVF) cycles. Almost unnoticed by profession and public, by 2016 they, however, reached lows not seen since 1996-1997. We here attempted to understand underlying causes for this decline. This study used publicly available IVF outcome data, reported by the CDC annually under Congressional mandate, involving over 90% of U.S. IVF centers and over 95% of U.S. IVF cycles. Years 2005, 2010, 2015 and 2016 served as index years, representing respectively, 27,047, 30,425, 21,771 and 19,137 live births in fnd IVF cycles. Concomitantly, the study associated timelines for introduction of new add-ons to IVF practice with changes in outcomes of fnd IVF cycles. Median female age remained at 36.0 years during the study period and center participation was surprisingly stable, thereby confirming reasonable phenotype stability. Main outcome measures were associations of specific IVF practice changes with declines in live IVF birth rates. Time associations were observed with increased utilization of "all-freeze" cycles (embryo banking), mild ovarian stimulation protocols, preimplantation genetic testing for aneuploidy (PGT-A) and increasing utilization of elective single embryo transfer (eSET). Among all add-ons, PGT-A, likely, affected fndIVF most profoundly. Though associations cannot denote causation, they can be hypothesis-generating. Here presented time-associations are compelling, though some of observed pregnancy and live birth loss may have been compensated by increases in frozen-thawed cycles and consequential pregnancies and live births not shown here. Pregnancies in frozen-thawed cycles, however, represent additional treatment cycles, time delays and additional costs. IVF live birth rates not seen since 1996-1997, and a likely continuous downward trend in U.S. IVF outcomes, therefore, mandate a reversal of current outcome trends, whatever ultimately the causes.

Micronized progesterone plus dydrogesterone versus micronized progesterone alone for luteal phase support in frozen-thawed cycles (MIDRONE): a prospective cohort study

STUDY QUESTION

Does the addition of oral dydrogesterone to vaginal progesterone as luteal phase support improve pregnancy outcomes during frozen embryo transfer (FET) cycles compared with vaginal progesterone alone?

SUMMARY ANSWER

Luteal phase support with oral dydrogesterone added to vaginal progesterone had a higher live birth rate and lower miscarriage rate compared with vaginal progesterone alone.

WHAT IS KNOWN ALREADY

Progesterone is an important hormone that triggers secretory transformation of the endometrium to allow implantation of the embryo. During IVF, exogenous progesterone is administered for luteal phase support. However, there is wide inter-individual variation in absorption of progesterone via the vaginal wall. Oral dydrogesterone is effective and well tolerated when used to provide luteal phase support after fresh embryo transfer. However, there are currently no data on the effectiveness of luteal phase support with the combination of dydrogesterone with vaginal micronized progesterone compared with vaginal micronized progesterone after FET.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study conducted at an academic infertility center in Vietnam from 26 June 2019 to 30 March 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We studied 1364 women undergoing IVF with FET. Luteal support was started when endometrial thickness reached ≥8 mm. The luteal support regimen was either vaginal micronized progesterone 400 mg twice daily plus oral dydrogesterone 10 mg twice daily (second part of the study) or vaginal micronized progesterone 400 mg twice daily (first 4 months of the study). In women with a positive pregnancy test, the appropriate luteal phase support regimen was continued until 7 weeks' gestation. The primary endpoint was live birth after the first FET of the started cycle, with miscarriage <12 weeks as one of the secondary endpoints.

MAIN RESULTS AND THE ROLE OF CHANCE

The vaginal progesterone + dydrogesterone group and vaginal progesterone groups included 732 and 632 participants, respectively. Live birth rates were 46.3% versus 41.3%, respectively (rate ratio [RR] 1.12, 95% CI 0.99-1.27, P = 0.06; multivariate analysis RR 1.30 (95% CI 1.01-1.68), P = 0.042), with a statistically significant lower rate of miscarriage at <12 weeks in the progesterone + dydrogesterone versus progesterone group (3.4% versus 6.6%; RR 0.51, 95% CI 0.32-0.83; P = 0.009). Birth weight of both singletons (2971.0 ± 628.4 versus 3118.8 ± 559.2 g; P = 0.004) and twins (2175.5 ± 494.8 versus 2494.2 ± 584.7; P = 0.002) was significantly lower in the progesterone plus dydrogesterone versus progesterone group.

LIMITATIONS, REASONS FOR CAUTION

The main limitations of the study were the open-label design and the non-randomized nature of the sequential administration of study treatments. However, our systematic comparison of the two strategies was able to be performed much more rapidly than a conventional randomized controlled trial. In addition, the single ethnicity population limits external generalizability.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings study suggest a role for oral dydrogesterone in addition to vaginal progesterone as luteal phase support in FET cycles to reduce the miscarriage rate and improve the live birth rate. Carefully planned prospective cohort studies with limited bias could be used as an alternative to randomized controlled clinical trials to inform clinical practice.

STUDY FUNDING/COMPETING INTERESTS

This study received no external funding. LNV has received speaker and conference fees from Merck, grant, speaker and conference fees from Merck Sharpe and Dohme, and speaker, conference and scientific board fees from Ferring; TMH has received speaker fees from Merck, Merck Sharp and Dohme, and Ferring; R.J.N. has received scientific board fees from Ferring and receives grant funding from the National Health and Medical Research Council (NHMRC) of Australia; BWM has acted as a paid consultant to Merck, ObsEva and Guerbet, and is the recipient of grant money from an NHMRC Investigator Grant.

TRIAL REGISTRATION NUMBER

NCT0399876.

The role of protein arginine methyltransferase 7 in human developmentally arrested embryos cultured in vitro

Human embryos of in vitro fertilization (IVF) are often susceptible to developmental arrest, which greatly reduces the efficiency of IVF treatment. In recent years, it has been found that protein arginine methyltransferase 7 (PRMT7) plays an important role in the process of early embryonic development. However, not much is known about the relationship between PRMT7 and developmentally arrested embryos. The role of PRMT7 in developmentally arrested embryos was thus investigated in this study. Discarded human embryos from IVF were collected for experimental materials. Quantitative real-time polymerase chain reaction (qRT-PCR) and confocal analyses were used to identify PRMT7 mRNA and protein levels in early embryos at different developmental stages, as well as changes in the methylation levels of H4R3me2s. Additionally, PRMT7 was knocked down in the developmentally arrested embryos to observe the further development of these embryos. Our results demonstrated that PRMT7 mRNA and protein levels in arrested embryos were significantly increased compared with those in control embryos; meanwhile, the methylation levels of H4R3me2s in arrested embryos were also increased significantly. Knockdown of PRMT7 could rescue partially developmentally arrested embryos, and even individual developmentally arrested embryos could develop into blastocysts. In conclusion, over-expression of PRMT7 disrupts the early embryo development process, leading to early embryos developmental arrest, but these developmentally arrested defects could be partially rescued by knockdown of the PRMT7 protein.

Letrozole-induced frozen embryo transfer cycles are associated with a lower risk of hypertensive disorders of pregnancy among women with polycystic ovary syndrome

BACKGROUND

Observational retrospective data suggest that an artificial cycle frozen embryo transfer may be associated with a higher risk of hypertensive disorder of pregnancy than a natural cycle frozen embryo transfer among women with regular ovulatory cycles. The corpus luteum, which is not present in the artificial frozen cycles, is at least partly responsible for this poor obstetrical outcome. However, an artificial cycle is the most frequently used regimen for women with polycystic ovary syndrome undergoing frozen embryo transfer. Whether the risk of hypertensive disorder of pregnancy could be mitigated by employing physiological frozen embryo transfer protocols that lead to the development of a corpus luteum in patients with polycystic ovary syndrome remains unknown.

OBJECTIVE

This study aimed to investigate the impact of letrozole use during frozen embryo transfer cycles on obstetrical and perinatal outcomes of singleton and twin pregnancies compared with artificial frozen cycles among women with polycystic ovary syndrome.

STUDY DESIGN

This retrospective cohort study involved women with polycystic ovary syndrome who had undergone artificial frozen cycles or letrozole-stimulated frozen cycles during the period from 2010 to 2018 at a tertiary care center. The primary outcome was the incidence of hypertensive disorder of pregnancy. A multivariable logistic regression analysis was performed to control for the relevant confounders.

RESULTS

A total of 2427 women with polycystic ovary syndrome were included in the final analysis. Of these women, 1168 underwent artificial cycles and 1259 underwent letrozole treatment, of which 25% of women treated with letrozole alone and 75% of women receiving letrozole combined with gonadotropins. After controlling for maternal characteristics and treatment variables, no significant difference was noticed regarding gestational diabetes mellitus, abnormal placentation, and preterm premature rupture of membranes between groups in both singleton and twin pregnancies. For birth outcomes, the prevalence rates of preterm birth, perinatal death, and birthweight outcomes were all comparable between groups in both singletons and twins. However, singleton pregnancies resulting from letrozole-stimulated cycles had a lower risk of hypertensive disorder of pregnancy than those conceived by artificial cycles (adjusted odds ratio, 0.63; 95% confidence interval, 0.40-0.98). Furthermore, a decreased risk of hypertensive disorder of pregnancy was seen among women with twin deliveries resulting from letrozole-stimulated cycles vs artificial cycles (adjusted odds ratio, 0.52; 95% confidence interval, 0.30-0.87). In addition, the cesarean delivery rate was significantly lower for singletons but not for twins in the letrozole group compared with pregnancies from the artificial cycle group (adjusted odds ratio, 0.63; 95% confidence interval, 0.50-0.78, and adjusted odds ratio, 1.20; 95% confidence interval, 0.65-2.23, respectively).

CONCLUSION

In women with polycystic ovary syndrome undergoing frozen embryo transfer, letrozole use for endometrial preparation was associated with a lower risk of hypertensive disorder of pregnancy than artificial cycles for endometrial preparation. Our findings provided a foundation that the increased risk of hypertensive disorder of pregnancy associated with frozen embryo transfer might be mitigated by utilizing physiological endometrial preparation protocols that lead to the development of a corpus luteum, such as a mild ovarian stimulation cycle for oligo- or anovulatory women.

Cumulative live birth rate after IVF: trend over time and the impact of blastocyst culture and vitrification

STUDY QUESTION

Has cumulative live birth rate (CLBR) improved over time and which factors are associated with such an improvement?

SUMMARY ANSWER

During an 11-year period, 2007–2017, CLBR per oocyte aspiration increased significantly, from 27.0% to 36.3%, in parallel with an increase in blastocyst transfer and cryopreservation by vitrification.

WHAT IS KNOWN ALREADY

While it has been shown that live birth rate (LBR) per embryo transfer (ET) is higher for fresh blastocyst than for fresh cleavage stage embryo transfer, CLBR per oocyte aspiration, including one fresh ET and all subsequent frozen embryo transfers (FET), does not seem to differ between the two culture strategies.

STUDY DESIGN, SIZE, DURATION

A national register study including all oocyte aspirations performed in Sweden from 2007 to 2017 (n = 124 700 complete IVF treatment cycles) was carried out. Oocyte donation cycles were excluded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were retrieved from the Swedish National Registry of Assisted Reproduction (Q-IVF) on all oocyte aspirations during the study period where autologous oocytes were used. CLBR was defined as the proportion of deliveries with at least one live birth per oocyte aspiration, including all fresh and/or frozen embryo transfers within 1 year, until one delivery with a live birth or until all embryos were used, whichever occurred first. The delivery of a singleton, twin, or other multiples was registered as one delivery. Cryopreservation of cleavage stage embryos was performed by slow freezing and of blastocyst by vitrification.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 124 700 oocyte aspirations were performed (in 61 313 women), with 65 304 aspirations in women <35 years and 59 396 in women ≥ 35 years, resulting in 38 403 deliveries with live born children. Overall, the CLBR per oocyte aspiration increased significantly during the study period, from 27.0% to 36.3% (odds ratio (OR) 1.039, 95% CI 1.035–1.043) and from 30.0% to 43.3% if at least one ET was performed (adjusted OR 1.055, 95% CI 1.050–1.059). The increase in CLBR was independent of maternal age, number of oocytes retrieved and number of previous IVF live births. The CLBR for women <35 and ≥35 years both increased significantly, following the same pattern. During the study period, a substantially increasing number of blastocyst transfers was performed, both in fresh and in FET cycles. Other important predicting factors for live birth, such as number of embryos transferred, could not explain the improvement. An increased single embryo transfer rate was observed with time.

LIMITATIONS, REASONS FOR CAUTION

The retrospective design implicates that other confounders of importance for CLBR cannot be ruled out. In addition, some FET cycles might be performed later than 1 year post oocyte aspiration for the last year (2017) and are, thus, not included in this study. In addition, no data on ‘dropouts’, i.e. patients that do not continue their treatment despite having cryopreserved embryos, are available, or if this drop-out rate has changed over time.

WIDER IMPLICATIONS OF THE FINDINGS

The results suggest that blastocyst transfer, particularly when used in FET cycles and in combination with vitrification, is an important contributor to the improved live birth rates over time. This gives a possibility for a lower number of oocyte aspirations needed to achieve a live birth and a shortened time to live birth.

STUDY FUNDING/COMPETING INTERESTS

The study was financed by grants from the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (ALFGBG-70940) and by Hjalmar Svensson’s research foundation. None of the authors declares any conflict of interest.

Comparison of Stimulated Cycles with Low Dose r-FSH versus Hormone Replacement Cycles for Endometrial Preparation Prior to Frozen-Thawed Embryo Transfer in Young Women with Polycystic Ovarian Syndrome: A Single-Center Retrospective Cohort Study from China

Objective

The principal purpose of this study was to compare reproductive outcomes for stimulated cycles (STC) and hormone replacement cycles (HRC) for endometrial preparation before frozen-thawed embryo transfer (FET) in young women with polycystic ovary syndrome (PCOS).

Methods

We conducted a retrospective study of 1434 FET cycles from January, 2017 to March, 2020 in our reproductive center, in which stimulated and hormone replacement cycles were used for endometrial preparation. Pregnancy outcomes of couples undergoing routine STC-FET or HRC-FET were analyzed by propensity score matching (PSM) and multivariable logistic regression analyses.

Results

Data on 1234 HRC protocols (86% of the total) and 200 STC protocols (14%) were collected. After PSM, 199 patients were included in both groups, respectively. There was no significant difference in positive pregnancy rate (52.7% vs 54.8%, p=0.763), clinical pregnancy rate (51.8% vs 52.8%, p=0.841), live birth rate (45.2% vs 43.7%, p=0.762), pregnancy loss rate (9.7% vs 16.2%, p=0.164) and ectopic pregnancy rate (1.5% vs 0.5%, p=0.615) between STC and HRC protocols. Subsequent multivariate logistic regression analysis also yielded similar results.

Conclusion

STC for endometrial preparation had similar pregnancy outcomes compared with HRC protocols. Evidence is available which shows that for young women with PCOS in preparation for FET, HRC could be a reasonable choice for patients who are unwilling to accept injections. However, STC may reduce unnecessary anxiety and operational costs and offer more flexibility for patients. Eventually, we must embrace the concepts of individualization, securitization, and optimization in the clinic.

Frozen embryo transfer and preeclampsia: where is the link?

PURPOSE OF REVIEW

Preeclampsia is the leading cause of maternal death and has a higher incidence in patients undergoing assisted reproduction treatments. New studies about the mechanisms by which it is more frequent in this population have emerged. The purpose of this review is to gather current information about the available results on this correlation and its possible physiopathology.

RECENT FINDINGS

Recent publications on the physiopathology of preeclampsia indicate that the corpus luteum is the main source of hormonal production until placental formation and that apart from the secretion of estrogen and progesterone, corpus luteum also produces important substances involved in maternal circulatory adaptation, such as relaxin.With the recent increasing number of frozen embryos transfer in natural cycles or under hormonal replacement, this adaptive circulatory process may be unbalanced and predispose this population to preeclampsia.

SUMMARY

This article provides a review of frozen embryo transfer and available protocols, the highest incidence of gestational hypertensive disorders presented by the infertile population and an overview of the possible impact of the absence of corpus luteum on the genesis of this disease.

Individual culture leads to decreased blastocyst formation but does not affect pregnancy outcomes in the setting of a single, vitrified-warmed euploid blastocyst transfer

PURPOSE

To evaluate embryology and pregnancy outcomes following individual and group embryo culture in the setting of contemporary laboratory practices and freeze-all cycles.

METHODS

Patients underwent ovarian stimulation followed by intracytoplasmic sperm injection (ICSI). Embryos proceeded through individual culture and then underwent preimplantation genetic testing for aneuploidy (PGT-A) via trophectoderm biopsy. In a subsequent cycle, participants underwent single embryo transfer of a vitrified-warmed, euploid embryo. Outcomes were compared to controls undergoing group culture during the same time frame. The Mann-Whitney U test and logistic regression models were utilized.

RESULTS

Outcomes were assessed for 144 patients whose embryos underwent individual culture and 449 controls whose embryos underwent group culture. There were no significant differences in fertilization rates between groups (81.7% for individual culture vs. 84.1% for group culture, p = 0.22). However, individual culture was associated with a decreased rate of blastocyst formation compared to group culture (43.5% vs. 48.5%, p < 0.01). Following single, vitrified-warmed euploid blastocyst transfer, there were no significant differences between individual culture and group culture, respectively, in rates of positive βhCG (81.9% vs. 81.5%, p = 0.91), sustained implantation (63.9% vs. 65.0%, p = 0.80), biochemical miscarriage (16.7% vs. 12.3%, p = 0.18), or clinical miscarriage (1.4% vs. 4.2%, p = 0.13).

CONCLUSION

While individual culture appears to negatively impact the rate of usable blastocyst formation compared to group culture, there were no significant differences in pregnancy outcomes following transfer of a single, vitrified-warmed euploid blastocyst.

Lower chromosomal abnormality frequencies in miscarried conceptuses from frozen blastocyst transfers in ART

STUDY QUESTION

Are blastocyst culture and cryopreservation in ART associated with chromosomal abnormalities in miscarried products of conception (POC)?

SUMMARY ANSWER

Frozen blastocyst transfer in women aged 35 years or older and frozen embryo transfer (ET) (including both cleavage-stage embryo and blastocyst) in women aged <35 years are associated with decreased frequencies of embryonic chromosomal abnormalities in miscarried POC.

WHAT IS KNOWN ALREADY

Blastocyst culture and embryo cryopreservation have been previously associated with favorable ART treatment outcomes and widely applied in clinical practice. However, the association between these embryo manipulation procedures and embryonic chromosomal abnormalities has not been evaluated to the best of our knowledge.

STUDY DESIGN, SIZE, DURATION

This retrospective study included a total of 720 patients who underwent IVF/ICSI, and the retained POC were obtained. A single-nucleotide polymorphism (SNP)-based chromosomal microarray analysis (CMA) of all miscarried conceptuses was performed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was based on the Clinical Reproductive Medicine Management System/Electronic Medical Record Cohort Database (CCRM/EMRCD) at our center. In total, 720 miscarried POCs were collected from patients undergoing ART (including fresh cleavage-stage ET, fresh blastocyst transfer, frozen cleavage-stage ET and frozen blastocyst transfer), and the incidences and profiles of cytogenetic abnormalities in the miscarried conceptuses were measured via SNP-based CMA.

MAIN RESULTS AND THE ROLE OF CHANCE

The chromosomal abnormality rate in POC varied from 33.7% to 66.7% among the different ET strategies. In the patients aged ≥35 years, frozen blastocyst transfer was significantly associated with a lower incidence of chromosomal aberrations in the POCs (adjusted odds ratio (aOR): 0.171 (95% CI: 0.040-0.738); P = 0.018) than fresh blastocyst transfer. In the patients aged <35 years, frozen ET was significantly associated with a lower incidence of chromosomal aberrations than fresh ET in both cleavage-stage ET cycles and blastocyst transfers cycles (aOR: 0.545 (0.338-0.879), P = 0.013; and aOR: 0.357 (0.175-0.730), P = 0.005, respectively). Trisomy was the most frequent abnormal embryonic karyotype in the different ET strategies, and its frequency significantly differed among strategies (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study was retrospectively designed, and we cannot draw any definite conclusions from our results regarding the adequate safety of embryo cryopreservation in ongoing pregnancy.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first study assessing the associations of ET strategies with the probability of miscarriage associated with embryonic chromosomal abnormalities. However, the underlying mechanism of these associations is unknown; this study may promote research concerning ET strategies and promote comprehensive consultations and recommendations for patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Natural Science Foundation of China (Grant No.81571409), Science and Technology Research Project of Henan (Grant No. 172102310009) and Medical Science and Technology Research Project of Henan (Grant No. 201701005). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Individualised luteal phase support in artificially prepared frozen embryo transfer cycles based on serum progesterone levels: a prospective cohort study

STUDY QUESTION

Does an individualised luteal phase support (iLPS), according to serum progesterone (P4) level the day prior to euploid frozen embryo transfer (FET), improve pregnancy outcomes when started on the day previous to embryo transfer?

SUMMARY ANSWER

Patients with low serum P4 the day prior to euploid FET can benefit from the addition of daily subcutaneous P4 injections (Psc), when started the day prior to FET, and achieve similar reproductive outcomes compared to those with initial adequate P4 levels.

WHAT IS KNOWN ALREADY

The ratio between FET/IVF has spectacularly increased in the last years mainly thanks to the pursuit of an ovarian hyperstimulation syndrome free clinic and the development of preimplantation genetic testing (PGT). There is currently a big concern regarding the endometrial preparation for FET, especially in relation to serum P4 levels around the time of embryo transfer. Several studies have described impaired pregnancy outcomes in those patients with low P4 levels around the time of FET, considering 10 ng/ml as one of the most accepted reference values. To date, no prospective study has been designed to compare the reproductive outcomes between patients with adequate P4 the day previous to euploid FET and those with low, but restored P4 levels on the transfer day after iLPS through daily Psc started on the day previous to FET.

STUDY DESIGN, SIZE, DURATION

A prospective observational study was conducted at a university-affiliated fertility centre between November 2018 and January 2020 in patients undergoing PGT for aneuploidies (PGT-A) IVF cycles and a subsequent FET under hormone replacement treatment (HRT). A total of 574 cycles (453 patients) were analysed: 348 cycles (leading to 342 euploid FET) with adequate P4 on the day previous to FET, and 226 cycles (leading to 220 euploid FET) under iLPS after low P4 on the previous day to FET, but restored P4 levels on the transfer day.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Overall we included 574 HRT FET cycles (453 patients). Standard HRT was used for endometrial preparation. P4 levels were measured the day previous to euploid FET. P4 > 10.6 ng/ml was considered as adequate and euploid FET was performed on the following day (FET Group 1). P4 < 10.6 ng/ml was considered as low, iLPS was added in the form of daily Psc injections, and a new P4 analysis was performed on the following day. FET was only performed on the same day when a restored P4 > 10.6 ng/ml was achieved (98.2% of cases) (FET Group 2).

MAIN RESULTS AND THE ROLE OF CHANCE

Patient's demographics and cycle parameters were comparable between both euploid FET groups (FET Group 1 and FET Group 2) in terms of age, weight, oestradiol and P4 levels and number of embryos transferred. No statistically significant differences were found in terms of clinical pregnancy rate (56.4% vs 59.1%: rate difference (RD) -2.7%, 95% CI [-11.4; 6.0]), ongoing pregnancy rate (49.4% vs 53.6%: RD -4.2%, 95% CI [-13.1; 4.7]) or live birth rate (49.1% vs 52.3%: RD -3.2%, 95% CI [-12; 5.7]). No significant differences were also found according to miscarriage rate (12.4% vs 9.2%: RD 3.2%, 95% CI [-4.3; 10.7]).

LIMITATIONS, REASONS FOR CAUTION

Only iLPS through daily Psc was evaluated. The time for Psc injection was not stated and no serum P4 determinations were performed once the pregnancy was achieved.

WIDER IMPLICATIONS OF THE FINDINGS

Our study provides information regarding an 'opportunity window' for improved ongoing pregnancy rates and miscarriage rates through a daily Psc injection in cases of inadequate P4 levels the day previous to FET (P4 < 10.6 ng/ml) and restored values the day of FET (P4 > 10.6 ng/ml). Only euploid FET under HRT were considered, avoiding one of the main reasons of miscarriage and implantation failure and overcoming confounding factors such as female age, embryo quality or ovarian stimulation protocols.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was received. B.C. reports personal fees from MSD, Merck Serono, Ferring Pharmaceuticals, IBSA and Gedeon Richter outside the submitted work. N.P. reports grants and personal fees from MSD, Merck Serono, Ferring Pharmaceuticals, Theramex and Besins International and personal fees from IBSA and Gedeon Richter outside the submitted work. The remaining authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

NCT03740568.

Transfer of fresh or frozen embryos: a randomised controlled trial

STUDY QUESTION

Is IVF with frozen-thawed blastocyst transfer (freeze-all strategy) more effective than IVF with fresh and frozen-thawed blastocyst transfer (conventional strategy)?

SUMMARY ANSWER

The freeze-all strategy was inferior to the conventional strategy in terms of cumulative ongoing pregnancy rate per woman.

WHAT IS KNOWN ALREADY

IVF without transfer of fresh embryos, thus with frozen-thawed embryo transfer only (freeze-all strategy), is increasingly being used in clinical practice because of a presumed benefit. It is still unknown whether this new IVF strategy increases IVF efficacy.

STUDY DESIGN, SIZE, DURATION

A single-centre, open label, two arm, parallel group, randomised controlled superiority trial was conducted. The trial was conducted between January 2013 and July 2015 in the Netherlands. The intervention was one IVF cycle with frozen-thawed blastocyst transfer(s) versus one IVF cycle with fresh and frozen-thawed blastocyst transfer(s). The primary outcome was cumulative ongoing pregnancy resulting from one IVF cycle within 12 months after randomisation. Couples were allocated in a 1:1 ratio to the freeze-all strategy or the conventional strategy with an online randomisation programme just before the start of down-regulation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were subfertile couples with any indication for IVF undergoing their first IVF cycle, with a female age between 18 and 43 years. Differences in cumulative ongoing pregnancy rates were expressed as relative risks (RR) with 95% CI. All outcomes were analysed following the intention-to-treat principle.

MAIN RESULTS AND THE ROLE OF CHANCE

Two-hundred-and-five couples were randomly assigned to the freeze-all strategy (n = 102) or to the conventional strategy (n = 102). The cumulative ongoing pregnancy rate per woman was significantly lower in women allocated to the freeze-all strategy (19/102 (19%)) compared to women allocated to the conventional strategy (32/102 (31%); RR 0.59; 95% CI 0.36-0.98).

LIMITATIONS, REASONS FOR CAUTION

As this was a single-centre study, we were unable to study differences in study protocols and clinic performance. This, and the limited sample size, should make one cautious in using the results as the basis for definitive policy. All patients undergoing IVF, including those with a poor prognosis, were included; therefore, the outcome could differ in women with a good prognosis of IVF treatment success.

WIDER IMPLICATIONS OF THE FINDINGS

Our results indicate that there might be no benefit of a freeze-all strategy in terms of cumulative ongoing pregnancy rates. The efficacy of the freeze-all strategy in subgroups of patients, different stages of embryo development, and different freezing protocols needs to be further established and balanced against potential benefits and harms for mothers and children.

STUDY FUNDING/COMPETING INTEREST(S)

The Netherlands Organisation for Health Research and Development (ZonMW grant 171101007). S.M., F.M. and M.v.W. stated they are authors of the Cochrane review 'Fresh versus frozen embryo transfers in assisted reproduction'.

TRIAL REGISTRATION NUMBER

Dutch Trial Register, NTR3187.

TRIAL REGISTRATION DATE

9 December 2011.

DATE OF FIRST PATIENT’S ENROLMENT

8 January 2013.

When Should We Freeze Embryos? Current Data for Fresh and Frozen Embryo Replacement IVF Cycles

Recent years have seen a dramatic rise in the number of frozen-thawed embryo replacement (FER) cycles. Along with the advances in embryo cryopreservation techniques, the optimization of endometrial receptivity has resulted in outcomes for FER that are similar to fresh embryo transfer. However, the question of whether the Freeze all strategy is for all is nowadays a hot topic. This review addresses this issue and describes current evidence based on randomized controlled trials and observational studies. To date, it is reasonable to perform FER in cases with a clear indication for the benefits of such strategy including impending ovarian hyperstimulation syndrome (OHSS) or preimplantation genetic testing for aneuploidy (PGT-A); however, this strategy does not fit for all. This review analyses the pros and cons of the freeze all strategy highlighting the need to follow a personalized plan in embryo transfer, avoiding a freeze all methodology for all patients in an unselected manner.

Frozen Embryo Transfer and Preeclampsia Risk

Worldwide, the use of Assisted Reproductive Technology (ART) has been steadily rising over recent years. With the continuous improvements in cryopreservation techniques and the growing practice of single embryo transfer, the proportion of frozen embryo transfer (FET) cycles has been increasing, therefore raising concern about the safety of this ART technique to both mothers and infants. This review aims to summarize the current evidence regarding the risk of preeclampsia in singleton pregnancies achieved by autologous FET compared to fresh embryo transfer, and to discuss the influence of different protocols used for endometrium preparation in frozen cycles on the risk of this obstetric complication. Several studies have reported a higher risk of hypertensive disorders, including preeclampsia, in pregnancies following FET compared with fresh embryo transfer. Recently, artificial FET cycles, which preclude the development of a corpus luteum, were shown to be associated with an increased preeclampsia risk in comparison with natural and stimulated cycles. Importantly, no difference was found between FET in a modified natural cycle and spontaneous conception. It has been proposed that the absence of the corpus luteum in artificial cycles may, at least partly, contribute to the observed increased risk of preeclampsia. Indeed, the corpus luteum secretes vasoactive hormones, such as relaxin, which are not replaced in artificial cycles, thereby compromising maternal cardiovascular adaptations to pregnancy, resulting in an increased risk of preeclampsia. If these findings are confirmed by a randomized controlled trial, natural, modified natural or stimulated cycles might be preferred over artificial cycles in eligible patients.

Single-embryo transfer: a key strategy to reduce the risk for multiple pregnancy in assisted human reproduction

In the early days of assisted reproductive technology (ART), the main target was achieving gestation. Success rates were low, and multiple embryo transfers became common practice, with multiple pregnancies being 20 times higher than in natural conception. Multiple pregnancy is associated with a higher risk of complications for the mother and the baby than a singleton pregnancy. Added to healthcare costs, multiple pregnancy also involves other costs and psychosocial risks, with a high social and health costs. At present, success rates of assisted human reproduction (AHR) have improved dramatically, partially due to advances in laboratory techniques such as culture of blastocyst-stage embryos and vitrification. Additionally, there is a wide range of counseling, health and economic policies that have demonstrated being effective in increasing single-embryo transfer (SET) practices and reducing multiple pregnancies, which ensures satisfactory success rates. Therefore, single-embryo transfer emerges as the approach of choice for AHR to result in a full-term healthy newborn.

The euploid blastocysts obtained after luteal phase stimulation show the same clinical, obstetric and perinatal outcomes as follicular phase stimulation-derived ones: a multicenter study

STUDY QUESTION

Are the reproductive outcomes (clinical, obstetric and perinatal) different between follicular phase stimulation (FPS)- and luteal phase stimulation (LPS)-derived euploid blastocysts?

SUMMARY ANSWER

No difference was observed between FPS- and LPS-derived euploid blastocysts after vitrified-warmed single embryo transfer (SET).

WHAT IS KNOWN ALREADY

Technical improvements in IVF allow the implementation non-conventional controlled ovarian stimulation (COS) protocols for oncologic and poor prognosis patients. One of these protocols begins LPS 5 days after FPS is ended (DuoStim). Although, several studies have reported similar embryological outcomes (e.g. fertilization, blastulation, euploidy) between FPS- and LPS-derived cohort of oocytes, information on the reproductive (clinical, obstetric and perinatal) outcomes of LPS-derived blastocysts is limited to small and retrospective studies.

STUDY DESIGN, SIZE, DURATION

Multicenter study conducted between October 2015 and March 2019 including all vitrified-warmed euploid single blastocyst transfers after DuoStim. Only first transfers of good quality blastocysts (≥BB according to Gardner and Schoolcraft's classification) were included. If euploid blastocysts obtained after both FPS and LPS were available the embryo to transfer was chosen blindly. The primary outcome was the live birth rate (LBR) per vitrified-warmed single euploid blastocyst transfer in the two groups. To achieve 80% power (α = 0.05) to rule-out a 15% difference in the LBR, a total of 366 first transfers were required. Every other clinical, as well as obstetric and perinatal outcomes, were recorded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Throughout the study period, 827 patients concluded a DuoStim cycle and among them, 339 did not identify any transferable blastocyst, 145 had an euploid blastocyst after FPS, 186 after LPS and 157 after both FPS and LPS. Fifty transfers of poor quality euploid blastocysts were excluded and 49 patients did not undergo an embryo transfer during the study period. Thus, 389 patients had a vitrified-warmed SET of a good quality euploid blastocyst (182 after FPS and 207 after LPS). For 126 cases (32%) where both FPS- and LPS-derived good quality blastocysts were available, the embryo transferred was chosen blindly with a 'True Random Number Generator' function where '0' stood for FPS-derived euploid blastocysts and '1' for LPS-derived ones (n = 70 and 56, respectively) on the website random.org. All embryos were obtained with the same ovarian stimulation protocol in FPS and LPS (GnRH antagonist protocol with fixed dose of rec-FSH plus rec-LH and GnRH-agonist trigger), culture conditions (continuous culture in a humidified atmosphere with 37°C, 6% CO2 and 5% O2) and laboratory protocols (ICSI, trophectoderm biopsy in Day 5-7 without assisted hatching in Day 3, vitrification and comprehensive chromosome testing). The women whose embryos were included had similar age (FPS: 38.5 ± 3.1 and LPS: 38.5 ± 3.2 years), prevalence of male factor, antral follicle count, basal hormonal characteristics, main cause of infertility and previous reproductive history (i.e. previous live births, miscarriages and implantation failures) whether the embryo came from FPS or LPS. All transfers were conducted after warming in an artificial cycle. The blastocysts transferred after FPS and LPS were similar in terms of day of full-development and morphological quality.

MAIN RESULTS AND THE ROLE OF CHANCE

The positive pregnancy test rates for FPS- and LPS-derived euploid blastocysts were 57% and 62%, biochemical pregnancy loss rates were 10% and 8%, miscarriage rates were 15% and 14% and LBRs were 44% (n = 80/182, 95% CI 37-51%) and 49% (n = 102/207, 95% CI 42-56%; P = 0.3), respectively. The overall odds ratio for live birth (LPS vs FPS (reference)) adjusted for day of blastocyst development and quality, was 1.3, 95% CI 0.8-2.0, P = 0.2. Among patients with euploid blastocysts obtained following both FPS and LPS, the LBRs were also similar (53% (n = 37/70, 95% CI 41-65%) and 48% (n = 27/56, 95% CI 35-62%) respectively; P = 0.7). Gestational issues were experienced by 7.5% of pregnant women after FPS- and 10% of women following LPS-derived euploid single blastocyst transfer. Perinatal issues were reported in 5% and 0% of the FPS- and LPS-derived newborns, respectively. The gestational weeks and birthweight were similar in the two groups. A 5% pre-term delivery rate was reported in both groups. A low birthweight was registered in 2.5% and 5% of the newborns, while 4% and 7% showed high birthweight, in FPS- and LPS-derived euploid blastocyst, respectively. Encompassing the 81 FPS-derived newborns, a total of 9% were small and 11% large for gestational age. Among the 102 LPS-derived newborns, 8% were small and 6% large for gestational age. No significant difference was reported for all these comparisons.

LIMITATIONS, REASONS FOR CAUTION

The LPS-derived blastocysts were all obtained after FPS in a DuoStim protocol. Therefore, studies are required with LPS-only, late-FPS and random start approaches. The study is powered to assess differences in the LBR per embryo transfer, therefore obstetric and perinatal outcomes should be considered observational. Although prospective, the study was not registered.

WIDER IMPLICATIONS OF THE FINDINGS

This study represents a further backing of the safety of non-conventional COS protocols. Therefore, LPS after FPS (DuoStim protocol) is confirmed a feasible and efficient approach also from clinical, obstetric and perinatal perspectives, targeted at patients who need to reach the transfer of an euploid blastocyst in the shortest timeframe possible due to reasons such as cancer, advanced maternal age and/or reduced ovarian reserve and poor ovarian response.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Varying levels of serum estradiol do not alter the timing of the early endometrial secretory transformation

STUDY QUESTION

Do supraphysiologic estradiol (E2) levels in the ranges attained during normal and high response superovulation cycles modify the onset of endometrial secretory transformation?

SUMMARY ANSWER

Highly supraphysiologic levels of E2 do not alter the ability of physiologic levels of progesterone (P4) to induce secretory transformation.

WHAT IS KNOWN ALREADY

Previous studies have demonstrated that premature P4 elevations during IVF cycles are associated with a decrement in clinical pregnancy rates after fresh embryo transfer due to shifts in the window of implantation (WOI). However, alterations in the onset of secretory transformation may not apply uniformly to all patients. High responders with supraphysiologic E2 levels accompanied by similar subtle increases in P4 have not been shown to have decreased sustained implantation rates. This prospective investigation in which whole-genome transcriptomic and methylomic analysis of the endometrium is performed for individual patients under a range of E2 concentrations brings clarity to a long-debated issue.

STUDY DESIGN, SIZE, DURATION

A randomized, prospective and paired trial was conducted in which 10 participants were enrolled and randomized to the order in which they completed three distinct uterine stimulation cycles, each at a specific E2 concentration: physiologic (∼180 pg/ml), moderately supraphysiologic (600-800 pg/ml) or supraphysiologic (2000 pg/ml). Target E2 ranges were selected to mimic those seen in natural, controlled ovarian stimulation and IVF cycles. E2 valerate was administered in order to maintain stable E2 levels for 12 days followed by intramuscular P4 in oil 10 mg/day for two doses, after which an endometrial biopsy was performed. A total of 30 endometrial biopsies were included in a whole-genome transcriptomic and methylomic analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Healthy volunteers without a history of infertility were included in this study at a single large infertility center. DNA was isolated from the endometrial biopsy specimens and bisulfite sequencing was performed to construct a methylation array. Differential methylation analysis was conducted based on differences in M-values of individuals across treatment groups for each probe as well as carrying out t-tests. RNA was isolated for RNA-Seq analysis and gene expression values were compared using DESeq2. All analyses were performed in a pairwise fashion to compare among the three stimulation cycles within individuals and secondarily to compare all participants in each of the cycles.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean peak E2 and P4 levels were 275 pg/ml and 4.17 ng/ml in the physiologic group, 910 pg/ml and 2.69 ng/ml in the moderate group was, and 2043 pg/ml and 2.64 ng/ml in the supraphysiologic group, respectively. Principal component analysis of 834 913 CpG sites was performed on M-values of individuals within the low, moderate and supraphysiologic conditions in a paired approach. There were no differences in genome-wide methylation within participants across E2 groups. A paired analysis revealed that gene expression profiles did not differ within the same individual at each of the three E2 levels. No significant alterations in gene expression as related to endometrial physiology were identified between the low, moderate and supraphysiologic groups in an inter-participant analysis.

LIMITATIONS, REASONS FOR CAUTION

Although each participant completed a physiologic cycle in which E2 levels were maintained in a range that would simulate a natural cycle, our findings are limited by lack of an unmedicated control to assess if there was a potential effect from E2V. Additionally, our results were obtained in fertile individuals, who may have a different endometrial response compared to an infertile population. Despite the whole genomic endometrial assessment and rigorous, paired study design, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Given that the endometrial response to P4 is unaffected by E2 levels in the supraphysiologic range, diminutions in implantation seen in stimulated cycles may result from embryonic-endometrial dyssynchrony following early P4 elevations or slowly blastulating embryos, which occur independently of the magnitude of the E2 rise.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Foundation for Embryonic Competence, Basking Ridge, NJ, USA. Dr E.S. reports consultancy work for The Foundation for Embryonic Competence, Basking Ridge, NJ, USA. The other authors declare no conflict of interests related to this topic.

TRIAL REGISTRATION NUMBER

NCT02458404.

Effects of different cycle regimens for frozen embryo transfer on perinatal outcomes of singletons

STUDY QUESTION

Does the endometrial preparation protocol for frozen embryo transfer (FET) have an impact on perinatal outcomes?

SUMMARY ANSWER

Singleton newborns from conceptions after an artificial FET cycle had a higher risk of being large for gestational age (LGA).

WHAT IS KNOWN ALREADY

Most previous studies have concentrated on the clinical pregnancy, miscarriage and live birth rates of different endometrial preparation protocols for FET. However, the impacts of these cycle regimens on perinatal outcomes including birthweight, gestational age (GA) and related outcomes require more investigation.

STUDY DESIGN, SIZE, DURATION

We retrospectively analysed all singletons conceived by women who underwent non-donor FET cycles between July 2014 and July 2017. The propensity score matching (PSM) method using nearest neighbour matching at a proportion of 1:1 was established to adjust for factors that influence the probability of receiving different FET cycle regimens. The main outcomes of the study included birthweight and its related outcomes, Z-score, low birthweight (LBW, <2500 g), small for gestational age (SGA, ≤10th percentile of referential birthweight), LGA (≥90th percentile of referential birthweight) and macrosomia (birthweight >4000 g). The study outcomes also included GA at birth, preterm delivery (<37 weeks), very preterm delivery (<32 weeks), very low birthweight (VLBW, <1500 g), term LBW (at 37 weeks of gestation or greater) and preterm LBW (at <37 weeks of gestation).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 9267 cycles with live-born singletons were included in the analysis in our centre between July 2014 and July 2017. Of these, 2224, 4299 and 2744 live-born singletons were conceived by natural cycle FET, stimulated cycle FET and artificial cycle FET, respectively. After PSM, 1947 cycles of natural cycle FET versus stimulated cycle FET, 1682 cycles of stimulated cycle FET versus artificial cycle FET and 2333 cycles of natural cycle FET versus artificial cycle FET were included in the analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A higher mean birthweight and Z-score were observed in the artificial cycle FET group than in the stimulated cycle FET group (P = 0.005; P = 0.004, respectively). Singleton newborns conceived after artificial cycle FET were more likely to be LGA than those born after natural cycle FET or stimulated cycle FET (19.92% versus 16.94% and 19.29% versus 16.12%, respectively). The adjusted ORs (95% CIs) were 1.25 (1.05, 1.49) for artificial cycle FET compared with natural cycle FET (P = 0.014) and 1.26 (1.08, 1.46) for artificial cycle FET compared with stimulated cycle FET (P = 0.003). Newborns conceived after stimulated cycle FET had a lower mean GA at birth and a lower mean birthweight than those born after natural cycle FET or artificial cycle FET. The stimulated cycle FET group had lower adjusted odds of being macrosomia than the natural cycle FET group. No significant differences between natural cycle FET and stimulated cycle FET were found for any of the other outcomes.

LIMITATIONS, REASONS FOR CAUTION

This study had the disadvantage of being retrospective, and some cases were excluded due to missing data. The original allocation process was not randomized, which may have introduced bias. We have chosen not to account for multiple comparisons in our statistical analysis.

WIDER IMPLICATIONS OF THE FINDINGS

LGA can have long-term consequences in terms of risk for disease, which means that the influences of artificial cycle FET are of clinical significance and deserve more attention. Furthermore, these findings are critical for clinicians to be able to make an informed decision when choosing an endometrial preparation method.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the National Natural Science Foundation of China (NSFC) (31770989 to Y.W.) and the Shanghai Ninth People's Hospital Foundation of China (JYLJ030 to Y.W.). None of the authors have any conflicts of interest to declare.

Antioxidants increase blastocyst cryosurvival and viability post-vitrification

STUDY QUESTION

What is the effect of antioxidants acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid (A3) in vitrification and warming solutions on mouse blastocyst development and viability?

SUMMARY ANSWER

The combination of three antioxidants in vitrification solutions resulted in mouse blastocysts with higher developmental potential in vitro and increased viability as assessed by both an outgrowth model in vitro and fetal development following uterine transfer.

WHAT IS KNOWN ALREADY

The antioxidant combination of acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid present in IVF handling and embryo culture media has significant beneficial effects on mouse embryo and fetal development, especially under oxidative stress.

STUDY DESIGN, SIZE, DURATION

The study was a laboratory-based analysis of an animal model. Rapid cooling through vitrification was conducted on F1 mouse blastocysts, with antioxidants (A3) supplemented in vitrification and/or warming solutions, followed by culture and embryo transfer.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Pronucleate oocytes were collected and cultured in groups to Day 4 blastocysts. Expanded blastocysts were vitrified and warmed in solutions with and without the A3 antioxidants and cultured for a further 24 h. Blastocyst cell number and allocation, apoptosis and histone acetylation levels were all quantified, and viability through outgrowths and transfers assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

Mouse blastocysts vitrified with no antioxidants had significantly lower cell numbers (P  < 0.001) and higher apoptotic cells (P  < 0.05) compared to non-vitrified embryos. Addition of combined A3 antioxidants to the vitrification and warming solutions resulted in a significant increase in inner cell mass cell (ICM) number (P  < 0.001) and total cell number (P  < 0.01), and an increase in outgrowth area (P < 0.05), which correlated with the increased fetal weight (P < 0.05), crown rump length (P < 0.05) and limb development (P < 0.05) determined following transfer compared to embryos with no antioxidants. Furthermore, while blastocyst vitrification significantly reduced acetylation levels (P < 0.05) compared to non-vitrified embryos, the inclusion of A3 antioxidants helped to ameliorate this.

LIMITATIONS, REASONS FOR CAUTION

Embryo development was only examined in the mouse.

WIDER IMPLICATIONS OF THE FINDINGS

Results in this study demonstrate that vitrification and warming of blastocysts have significant detrimental effects on embryo histone acetylation and subsequent viability. The presence of antioxidants in the vitrification solutions helps to alleviate the negative effects of cryopreservation. Our data indicate that antioxidants need to be present in the medium at the time of exposure to increased oxidative stress associated with vitrification and that prior exposure (i.e. during culture or IVF alone) is insufficient to protect cells against cryo-induced injury. Hence, A3 antioxidants may assist in maintaining the viability of vitrified human embryos in ART through the reduction of oxidative stress.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Follicular-phase endometrial scratching: a truncated randomized controlled trial

STUDY QUESTION

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

SUMMARY ANSWER

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

WHAT IS KNOWN ALREADY

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

STUDY DESIGN, SIZE, DURATION

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

PARTICIPANTS/MATERIALS, SETTING, METHODS

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

MAIN RESULTS AND THE ROLE OF CHANCE

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

LIMITATIONS, REASONS FOR CAUTION

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

WIDER IMPLICATIONS OF THE FINDINGS

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

STUDY FUNDING/COMPETING INTEREST(S)

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

The effect of Day 3 cell number on pregnancy outcomes in vitrified-thawed single blastocyst transfer cycles

STUDY QUESTION

Does cell number on Day 3 have an impact on pregnancy outcomes in vitrified-thawed single blastocyst transfer cycles?

SUMMARY ANSWER

A low Day 3 cell number (≤5 cells) was independently associated with decreased live birth rate (LBR) during single blastocyst transfer cycles in young women.

WHAT IS KNOWN ALREADY

Day 3 cell number is an effective predictor of IVF success rates when transferring cleavage stage embryos. However, the association between Day 3 blastomere number and pregnancy outcomes after blastocyst transfer is still unknown.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study of 3543 patients who underwent frozen-thawed single blastocyst transfers from January 2013 to June 2018 at a tertiary-care academic medical center.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients were grouped into six groups according to the Day 3 cell number: ≤4 cells, 5 cells, 6 cells, 7 cells, 8 cells and >8 cells. The primary outcome measure was LBR. A logistic regression analysis was performed to explore the independent association between Day 3 blastomere number and LBR after adjustment for some potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

In women <35 years old, the LBR varied significantly according to Day 3 cell number, with the rate of 31.2%, 34.4%, 41.9%, 45.1%, 48.1% and 48.2% for the ≤4-cell, 5-cell, 6-cell, 7-cell, 8-cell and >8-cell groups, respectively (P < 0.001). This significant difference was also observed in the high- and low-quality blastocyst subgroups of young women. However, for women ≥35 years old, the rate of live birth was similar between groups. Furthermore, after accounting for confounding factors, the LBR was significantly decreased in the ≤4-cell (adjusted odds ratio (aOR): 0.62, 95% CI: 0.48-0.80, P < 0.001) and 5-cell (aOR: 0.73, 95% CI: 0.57-0.92, P = 0.009) groups as compared to the 8-cell group. Likewise, the blastocysts arising from ≤4-cell (aOR: 0.73, 95% CI: 0.57-0.93, P = 0.010) or 5-cell (aOR: 0.77, 95% CI: 0.61-0.97, P = 0.024) embryos were associated with lower clinical pregnancy rate than those from 8-cell embryos. No significant differences were observed in biochemical pregnancy rate and miscarriage rate.

LIMITATIONS, REASONS FOR CAUTION

A limitation of the current study was its retrospective design. Future prospective studies are needed to confirm our findings.

WIDER IMPLICATIONS OF THE FINDINGS

Our observations suggested that a low Day 3 cell number was related to decreased LBR after blastocyst transfer in young women, which provided vital information for clinicians in selecting blastocyst during IVF treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (NSFC) (31770989 to Y.W.; 81671520 to Q.C.) and the Shanghai Ninth People's Hospital Foundation of China (JYLJ030 to Y.W.). The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Prenatal growth trajectories and birth outcomes after frozen-thawed extended culture embryo transfer and fresh embryo transfer: the Rotterdam Periconception Cohort

RESEARCH QUESTION

Are there differences in prenatal growth trajectories and birth outcomes between singleton pregnancies conceived after IVF treatment with frozen-thawed extended culture embryo transfer at day 5, fresh embryo transfer at day 3 or naturally conceived pregnancies?

DESIGN

From a prospective hospital-based cohort, 859 singleton pregnancies were selected, including 133 conceived after IVF with frozen-thawed embryo transfer, 276 after fresh embryo transfer, and 450 naturally conceived pregnancies. Longitudinal 3D ultrasound scans were performed at 7, 9 and 11 weeks of gestation for offline crown-rump length (CRL) and embryonic volume measurements. Second trimester estimated fetal weight was based on growth parameters obtained during the routine fetal anomaly scan at 20 weeks of gestation. Birth outcome data were collected from medical records.

RESULTS

No differences regarding embryonic growth trajectories were observed between frozen-thawed and fresh embryo transfer. Birthweight percentiles after fresh embryo transfer were lower than after frozen-thawed embryo transfer (38.0 versus 48.0; P = 0.046, respectively). The prevalence of non-iatrogenic preterm birth (PTB) was significantly lower in pregnancies resulting from fresh embryo transfer compared with frozen-thawed embryo transfer (4.7% versus 10.9%; P = 0.026, respectively). Compared with naturally conceived pregnancies, birthweight percentiles and percentage of non-iatrogenic PTB were significantly lower in pregnancies after fresh embryo transfer and gestational age at birth was significantly higher.

CONCLUSIONS

This study shows that embryonic growth is comparable between singleton pregnancies conceived after fresh and frozen-thawed embryo transfer. The lower relative birthweight and PTB rate in pregnancies after fresh embryo transfer than after frozen-thawed embryo transfer and naturally conceived pregnancies warrants further investigation.

Do Strategies Favoring Frozen-thawed Embryo Transfer Have an Impact on Differences in IVF Success Rate, Multiple Pregnancy Rate, and Cost per Live Birth Between Fertility Clinics?

The aim of this retrospective cohort study is to establish whether strategies favoring frozen-thawed embryo transfer (FET) have an impact on differences in cumulative live birth rate (CLBR), weighted mean cost per live birth, and multiple pregnancy rate (MPR) between fertility clinics. Data were extracted from the Assisted Reproductive Technology (ART) Italian National Registry and refer to classical IVF or intracytoplasmic sperm injection (ICSI) cycles performed in 2018 in public funded Lombardy region fertility clinics. Propensity to FET cycles was expressed with the so-called freezing tendency index (FTI): [(No. of FETs + No. of transfers of embryos obtained from frozen-thawed oocytes) / (No. of fresh ETs + No. of canceled IVF cycles + Numerator)] × 100. Fertility clinics were divided according to their FTI: group A (FTI: 0-20%); group B (FTI: 20-40%); and group C (FTI: 40-60%). Groups A, B, and C included 6, 8, and 8 fertility clinics, respectively. The CLBR (95% CI) per started COH cycle was 13.1% (11.8-14.5%) in group A, 19.6% (18.6-20.7%) in group B, and 27.8% (26.8-28.9%) in group C (p < 0.0001). The weighted mean live birth cost was 32,770 ± 10,662 € in group A, 25,863 ± 11,510 € in group B, and 20,426 ± 3788 € in group C (p < 0.0001). The MPR (95% CI) was 15.4% (12.1-19.4%) in group A, 10.2% (8.7-12.1%) in group B (p = 0.0065), and 6.3% (5.2-7.6%) in group C (p = 0.0001). In conclusion, our results suggest that strategies favoring FET cycles are associated with an increased CLBR, a decreased weighted mean cost per live birth, and a decreased MPR.

Blastocyst Vitrification and Trophectoderm Biopsy Cumulatively Alter Embryonic Gene Expression in a Mouse Model

Although embryo vitrification has been used extensively in human assisted reproductive technology (ART) and animal models, epidemiologic evidence and randomized controlled trials suggest differences in pregnancy/perinatal outcomes (birthweight, risk for preterm birth, and pre-eclampsia) between babies born from fresh versus frozen embryo transfers. To address the uncertainty surrounding the effects of laboratory manipulations of embryos on clinical outcomes, we subjected mouse blastocysts to increasing levels of manipulation for transcriptome analysis. Blastocysts were randomly divided into four groups: no manipulation (control), single vitrification/thaw (1 vit), double vitrification/thaw (2 vit), and single vitrification/thaw plus trophectoderm biopsy and again vitrified/thawed (2 vit + bx). Three sets of 15 blastocysts in each group were pooled for RNA sequencing, and differentially expressed genes (DEGs) and pathways were determined by statistical analysis. Blastocysts were also stained for ZO-1 and F-actin to assess cytoskeletal integrity. Freeze/thaw and biopsy manipulation affected multiple biological pathways. The most significant differences were detected in genes related to innate immunity, apoptosis, and mitochondrial function, with the magnitude of change proportional to the extent to manipulation. Significant disruptions were also seen in cytoskeletal staining, with greater disruptions seen with greater of manipulation. Our data suggests that embryo vitrification and biopsy affect embryo gene transcription, with several identified DEGs that may have plausible mechanisms for the clinical outcomes seen in human offspring following ART. Further study is required to determine whether these alterations in gene expression are associated with clinical differences seen in children born from fresh or frozen embryo transfer.

Fresh embryo transfer versus freeze-only after in vitro maturation with a pre-maturation step in women with high antral follicle count: a randomized controlled pilot study

PURPOSE

In vitro maturation (IVM) is an alternative to in vitro fertilization (IVF) for women at high risk of developing ovarian hyperstimulation syndrome (OHSS). This study determined the effectiveness and safety of a freeze-only strategy versus fresh embryo transfer (ET) after IVM with a pre-maturation step (CAPA-IVM) in women with a high antral follicle count (AFC).

METHODS

This randomized, controlled pilot study (NCT04297553) was conducted between March and November 2020. Forty women aged 18-37 years with a high AFC (≥24 follicles in both ovaries) undergoing one cycle of CAPA-IVM were randomized to a freeze-only strategy with subsequent frozen ET (n = 20) or to fresh ET (n = 20). The primary endpoint was ongoing pregnancy resulting in live birth after the first ET of the started treatment cycle.

RESULTS

The ongoing pregnancy rate in the freeze-only group (65%) was significantly higher than that in the fresh ET group (25%; p = 0.03), as was the live birth rate (60% versus 20%; p = 0.02). Clinical pregnancy rate was numerically, but not significantly, higher after frozen versus fresh ET (70% versus 35%; p = 0.06), while the number of day 3 or good quality embryos, endometrial thickness on the day of oocyte pick-up, implantation rate, and positive pregnancy test rate did not differ significantly between groups. No cases of OHSS were observed, and miscarriage and multiple pregnancy rates were similar in the two groups.

CONCLUSIONS

These findings suggest that the effectiveness of CAPA-IVM could be improved considerably by using a freeze-only strategy followed by frozen ET in subsequent cycles.

TRIAL REGISTRATION NUMBER

NCT04297553 ( www.clinicaltrials.gov ).