Fresh embryo transfer versus frozen embryo transfer in in vitro fertilization cycles: a systematic review and meta-analysis

Embryo transfer impact: a comprehensive national cohort analysis comparing maternal and neonatal outcomes across varied embryo stages in fresh and frozen transfers

Introduction

The utilization of frozen embryo transfer not only enhances reproductive outcomes by elevating the likelihood of live birth and clinical pregnancy but also improves safety by mitigating the risks associated with ovarian hyperstimulation syndrome (OHSS) and multiple pregnancies. There has been an increasing debate in recent years regarding the advisability of making elective frozen embryo transfer the standard practice. Our study aims to determine the optimal choice between fresh and frozen embryo transfer, as well as whether the transfer should occur at the cleavage or blastocyst stage.

Method

In this retrospective cohort study conducted in Taiwan, data from the national assisted reproductive technology (ART) database spanning from January 1st, 2013, to December 31st, 2017, were analyzed. The study included 51,762 eligible female participants who underwent ART and embryo transfer. Pregnancy outcomes, maternal complications, and singleton neonatal outcomes were evaluated using the National Health Insurance Database from January 1st, 2013, to December 31st, 2018. Cases were categorized into groups based on whether they underwent fresh or frozen embryo transfers, with further subdivision into cleavage stage and blastocyst stage transfers. Exposure variables encompassed clinical pregnancy rate, live birth rate, OHSS, pregnancy-induced hypertension, gestational diabetes mellitus (DM), placenta previa, placental abruption, preterm premature rupture of membranes (PPROM), gestational age, newborn body weight, and route of delivery.

Results

Frozen blastocyst transfers showed higher rates of clinical pregnancy (CPR) and live births (LBR) compared to fresh blastocyst transfers. Conversely, frozen cleavage stage transfers demonstrated lower rates of clinical pregnancy and live birth compared to fresh cleavage stage transfers. Frozen embryo transfers were associated with reduced risks of OHSS but were linked to a higher risk of pregnancy-induced hypertension compared to fresh embryo transfers. Additionally, frozen embryo transfers were associated with a higher incidence of large for gestational age infants and a lower incidence of small for gestational age infants.

Conclusion

The freeze-all strategy may not be suitable for universal application. When embryos can develop to the blastocyst stage, FET is a favorable choice, but embryos can only develop to the cleavage stage, fresh embryo transfer becomes a more reasonable option.

The impact of reference growth standards on small- and large-for-gestational age outcomes among pregnancies conceived by fresh and frozen embryo transfers

Objective

To describe differences in the frequency of small-for-gestational age (SGA) and large-for-gestational age (LGA) driven by different birth weight curves in assisted reproductive technology (ART)-conceived pregnancies.

Design

Retrospective cohort study.

Setting

Single academic medical center.

Patients

Singleton live births between the gestational ages of 36 weeks and 0 days and 42 weeks and 6 days from fresh or frozen embryo transfer (ET).

Interventions

None.

Main Outcome Measures

SGA (<10th percentile) and LGA (>90th percentile) classified by Fenton, INTERGROWTH-21, World Health Organization, Duryea, and Oken curves.

Results

The median birth weight and gestational age at birth among fresh ET pregnancies were 3,289g (interquartile range [IQR], 2,977-3,600g) and 39.4 (IQR, 38.6-40.3) weeks, respectively, and those among frozen ET pregnancies were 3,399g (IQR, 3,065-3,685g) and 39.4 (IQR, 38.7-40.1) weeks, respectively. The frequencies of SGA neonates using each birth weight standard ranged from 5.8% to 13.4% for fresh ET and from 3.5% to 8.7% for frozen ET. Those of LGA neonates ranged from 5.3% to 14.3% for fresh ET and from 6.6% to 21.2% for frozen ET.

Conclusion

The frequency of SGA and LGA neonates among ART-conceived gestations is partially driven by the birth weight standard. Selecting an appropriate standard that best reflects the patient population is critical to quantifying the risk of ART-conceived pregnancies.

Association between the length of in vitro embryo culture, mode of ART, and the initial endogenous hCG rise in ongoing singleton pregnancies

STUDY QUESTION

Is there an association between the length of in vitro culture, mode of ART and the initial endogenous hCG rise, in cycles with a foetal heartbeat after single embryo transfer (ET) and implantation?

SUMMARY ANSWER

Both the length of in vitro culture and the mode of ART have an impact on the initial endogenous rise in hCG in singleton pregnancies.

WHAT IS KNOWN ALREADY

Different factors have been identified to alter the kinetics of hCG in pregnancies. Current studies show conflicting results regarding the kinetics of hCG after different types of ART (fresh vs frozen ET (FET)), the inclusion or not of preimplantation genetic testing (PGT), and the length of time in in vitro culture.

STUDY DESIGN, SIZE, DURATION

This was a multicentre cohort study, using prospectively collected data derived from 4938 women (5524 treatment cycles) undergoing IUI (cycles, n = 608) or ART (cycles, n = 4916) treatments, resulting a in singleton ongoing pregnancy verified by first-trimester ultrasound scan. Data were collected from the Danish Medical Data Centre, used by the three participating Danish public fertility clinics at Copenhagen University hospitals: Herlev Hospital, Hvidovre Hospital, and Rigshospitalet, from January 2014 to December 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The fresh ET cycles included cleavage-stage (2 or 3 days in vitro) and blastocyst (5 days in vitro) transfers. FET cycles included cleavage-stage (3 days in vitro before cryopreservation) or blastocyst (5 or 6 days in vitro before cryopreservation) transfers. The IUI cycles represented no time in vitro. To attain a comparable interval for serum-hCG (s-hCG), the ovulation induction time was identical: 35-37 h before oocyte retrieval or IUI. The conception day was considered as: the insemination day for pregnancies conceived after IUI, the oocyte retrieval day for fresh ET, or the transfer day minus 3 or 5 as appropriate for FET of Day 3 or 5 embryos. Multiple linear regression analysis was used, including days post-conception for the hCG measurement as a covariate, and was adjusted for the women's age, the cause of infertility, and the centre. For FET, a sensitivity analysis was used to adjust for endometrial preparation.

MAIN RESULTS AND THE ROLE OF CHANCE

The study totally includes 5524 cycles: 2395 FET cycles, 2521 fresh ET cycles, and 608 IUI cycles. Regarding the length of in vitro culture, with IUI as reference (for no time in in vitro culture), we found a significantly lower s-hCG in pregnancies achieved after fresh ET (cleavage-stage ET or blastocyst transfer). S-hCG was 18% (95% CI: 13-23%, P < 0.001) lower after fresh cleavage-stage ET, and 23% (95% CI: 18-28%, P < 0.001) lower after fresh blastocyst transfer compared to IUI. In FET cycles, s-hCG was significantly higher after blastocyst transfers compared to cleavage-stage FET, respectively, 26% (95% CI: 13-40%, P < 0.001) higher when cryopreserved on in vitro Day 5, and 14% (95% CI: 2-26%, P = 0.02) higher when cryopreserved on in vitro Day 6 as compared to Day 3. Regarding the ART treatment type, s-hCG after FET blastocyst transfer (Day 5 blastocysts) cycles was significantly higher, 33% (95% CI: 27-45%, P < 0.001), compared to fresh ET (Day 5 blastocyst), while there was no difference between cleavage-stage FET (Days 2 + 3) and fresh ET (Days 2 + 3). S-hCG was 12% (95% CI: 4-19%, 0.005) lower in PGT FET (Day 5 blastocysts) cycles as compared to FET cycles without PGT (Day 5 blastocysts).

LIMITATIONS, REASONS FOR CAUTION

The retrospective design is a limitation which introduces the risk of possible bias and confounders such as embryo score, parity, and ovarian stimulation.

WIDER IMPLICATIONS OF THE FINDINGS

This study elucidates how practices in medically assisted reproduction treatment are associated with the hCG kinetics, underlining a potential impact of in vitro culture length and mode of ART on the very early embryo development and implantation. The study provides clinicians knowledge that the type of ART used may be relevant to take into account when evaluating s-hCG for the prognosis of the pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study. AP has received consulting fees, research grants, or honoraria from the following companies: Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos, Merck A/S, and Organon. AZ has received grants and honoraria from Gedeon Richter. NLF has received grants from Gedeon Richter, Merck A/S, and Cryos. MLG has received honoraria fees or research grants from Gedeon Richter, Merck A/S, and Cooper Surgical. CB has received honoraria from Merck A/S. MB has received research grants and honoraria from IBSA. MPR, KM, and PVS all report no conflicts of interest.

TRIAL REGISTRATION NUMBER

The study was registered and approved by the Danish Protection Agency, Capital Region, Denmark (Journal-nr.: 21019857). No approval was required from the regional ethics committee according to Danish law.

Double vitrification and warming of blastocysts does not affect pregnancy, miscarriage or live birth rates

RESEARCH QUESTION

Does double blastocyst vitrification and warming affect pregnancy, miscarriage or live birth rates, or birth outcomes, from embryos that have undergone preimplantation genetic testing for aneuploidies (PGT-A) testing?

DESIGN

This retrospective observational analysis of embryo transfers was performed at a single centre between January 2017 and August 2022. The double-vitrification group included frozen blastocysts that were vitrified after 5-7 days of culture, warmed, biopsied (either once or twice) and re-vitrified. The single vitrification (SV) group included fresh blastocysts that were biopsied at 5-7 days and then vitrified.

RESULTS

A comparison of the 84 double-vitrification blastocysts and 729 control single-vitrification blastocysts indicated that the double-vitrification embryos were frozen later in development and had expanded more than the single-vitrification embryos. Of the 813 embryo transfer procedures reported, 452 resulted in the successful delivery of healthy infants (56%). There were no significant differences between double-vitrification and single-vitrification embryos in the pregnancy, miscarriage or live birth rates achieved after single-embryo transfer (55% versus 56%). Logistic regression indicated that while reduced live birth rates were associated with increasing maternal age at oocyte collection, longer culture prior to freezing and lower embryo quality, double vitrification was not a significant predictor of live birth rate.

CONCLUSIONS

Blastocyst double vitrification was not shown to impact pregnancy, miscarriage or live birth rates. Although caution is necessary due to the study size, no effects of double vitrification on miscarriage rates, birthweight or gestation period were noted. These data offer reassurance given the absence of the influence of double vitrification on all outcomes after PGT-A.

Natural proliferative phase frozen embryo transfer-a new approach which may facilitate scheduling without hindering pregnancy outcomes

STUDY QUESTION

How does a natural proliferative phase (NPP) strategy for frozen embryo transfer (FET) compare with the conventional artificial (AC) and natural (NC) endometrial preparation protocols in terms of live birth rates (LBR)?

SUMMARY ANSWER

This study supports the hypothesis that, just as for NC, NPP-FET may be a superior alternative to AC in terms of LBR.

WHAT IS KNOWN ALREADY

Although FETs are increasing worldwide, the optimal FET protocol is still largely controversial. Despite recent evidence supporting a possibly higher efficacy and safety of NC FETs, their widespread use is limited by the difficulties encountered during cycle monitoring and scheduling.

STUDY DESIGN, SIZE, DURATION

In this single center retrospective cohort study, we describe the NPP-FET protocol, in which vaginal progesterone is initiated during the proliferative phase as soon as an endometrium with a thickness of at least 7 mm is identified and ovulation is ruled out, regardless of mean diameter of the dominant follicle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

For comparison, we considered all blastocyst stage FET cycles preformed at a private infertility center between January 2010 and June 2022, subdivided according to the following subgroups of endometrial preparation: AC, NPP, and NC. We performed multivariable generalized estimating equations regression analysis to account for the following potential confounding variables: oocyte age at retrieval, oocyte source (autologous without preimplantation genetic testing for aneuploidies (PGT-A) versus autologous with PGT-A versus donated), number of oocytes retrieved/donated, embryo developmental stage (Day 5 versus Day 6), number of embryos transferred, quality of the best embryo transferred, and year of treatment. The main outcome measure was LBR. The secondary outcomes included hCG positive, clinical pregnancy and miscarriage rates, and the following perinatal outcomes: first trimester bleeding, second/third trimester bleeding, preterm rupture of membranes, gestational diabetes, gestational hypertensive disorders (GHD), and gestational age at delivery.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 5791 FET cycles were included in this analysis (2226 AC, 349 NPP, and 3216 NC). The LBR for FET was lower in the AC subgroup when compared to the NPP and NC (38.4%, 49.1%, and 45.2%, respectively; P < 0.01 AC versus NPP and AC versus NC). The rates of miscarriage were also lower in the NPP and NC subgroups when compared to AC (19.7%, 25.0%, and 34.9%, respectively; P < 0.01 NPP versus AC and NC versus AC). Considering perinatal outcomes, NPP-FET and NC were associated with a significantly lower first trimester bleeding compared to AC (17.3%, 14.7%, and 37.6%, respectively; P < 0.01 NPP versus AC and NC versus AC). Additionally, NC was associated with a lower rate of GHD when compared with AC (8.6% versus 14.5%, P < 0.01), while the rate following NPP-FET was 9.4%.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by its retrospective design. Moreover, there was also a low number of patients in the NPP subgroup, which may have led the study to be underpowered to detect clinically relevant differences between the subgroups.

WIDER IMPLICATIONS OF THE FINDINGS

Our study posits that the NPP-FET protocol may be an effective and safe alternative to both NC and AC, while still allowing for enhanced practicality in patient follow-up and FET scheduling. Further investigation on NPP-FET is warranted, with prospective studies including a larger and more homogeneous subsets of patients.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the IVI-RMA-Lisbon (2008-LIS-053-CG). The authors did not receive any funding for this study. The authors have no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

In Vitro Fertilization and Adverse Pregnancy Outcomes in the Elective Single Embryo Transfer Era

OBJECTIVE

Our objective was to estimate the association between in vitro fertilization (IVF) pregnancy and adverse pregnancy outcomes during delivery hospital admission in a contemporary, nation-wide cohort of births in the United States.

STUDY DESIGN

This retrospective, population-based cohort study used the National Inpatient Sample database to identify patients discharged from the hospital following delivery from 2014 to 2019. IVF pregnancies were identified using the International Classification of Disease-Revision 9/10 codes. Crude and adjusted odds ratios of preterm birth and other clinically significant adverse pregnancy outcomes were evaluated using multivariable logistic regression models. Trends in preterm birth and multiple pregnancy were estimated over the study period. The contribution of multiple pregnancy to preterm birth in IVF pregnancy was estimated in a mediation analysis.

RESULTS

Among 4,451,667 delivery-related discharges, IVF pregnancies were associated with 3.25 times the odds of preterm birth (95% confidence interval [CI]: 3.05-3.46, p < 0.001) compared with non-IVF pregnancy deliveries. Odds of preterm birth in IVF pregnancy delivery discharges decreased over the study period (p-value for linear trend = 0.009). The proportion of multiple pregnancies decreased in IVF pregnancy delivery discharges but remained stable in non-IVF pregnancy deliveries. The proportion of the adjusted effect of IVF pregnancy on preterm birth mediated through multiple pregnancy was 67.6% (95% CI: 62.6-72.7%).

CONCLUSION

While the odds of adverse pregnancy outcomes are increased compared with non-IVF pregnancies, the odds of preterm birth and multiple gestation have decreased among IVF pregnancies in the United States.

KEY POINTS

· Pregnancies conceived by in vitro fertilization (IVF) are at significantly higher risk of multiple gestation, preterm birth, and other pregnancy complications.. · Recent guidelines for artificial reproductive treatments recommend single-embryo transfer in IVF.. · Using population-wide data, we demonstrate a significant gradual decline in the rates of preterm birth and other pregnancy complications following IVF in the last decade, mostly mediated by a reduction in multiple pregnancies..

Impact of vaginal microecological differences on pregnancy outcomes and endometrial microbiota in frozen embryo transfer cycles

PURPOSE

This prospective study investigates the correlation between vaginal microecology and pregnancy outcomes and explores their impact on endometrial microbiota composition during frozen embryo transfer (FET) cycles. Additionally, the impact of transvaginal Lactobacillus supplementation on reproductive outcomes in patients with previous failed cycles was assessed.

METHODS

A total of 379 patients undergoing FET at a reproductive medicine center were categorized into clinical pregnancy (CP), miscarriage (MISC), and non-pregnant (NP) groups. Vaginal specimens were collected for microecological evaluation prior to embryo transfer. Endometrial microbiota samples were obtained during embryo transfer for 16S rRNA gene sequencing analysis to assess endometrial microbiota composition. Vaginal microecological indicators, including pH, Lactobacillus dominance, and leukocyte esterase activity, were measured. Transvaginal Lactobacillus supplementation was investigated in 60 patients with previous failed cycles.

RESULTS

Vaginal microecology significantly correlated with pregnancy outcomes, with normal microecology associated with a higher clinical pregnancy rate. Vaginal pH and leukocyte esterase activity were significantly associated with clinical pregnancy. Furthermore, vaginal microecological differences significantly impacted endometrial microbiota composition. However, no significant differences were observed in endometrial microbiota composition among the CP, MISC, and NP groups. Notably, transvaginal Lactobacillus supplementation increased the clinical pregnancy rate without affecting the miscarriage rate.

CONCLUSION

This study highlights that normal vaginal microecology, characterized by lower pH and leukocyte esterase negativity, is associated with a higher likelihood of clinical pregnancy following FET. Importantly, vaginal microecological differences influence endometrial microbiota composition. Moreover, transvaginal Lactobacillus supplementation appears promising in improving clinical pregnancy rates in patients with previous failed cycles. These findings contribute to a better understanding of the interplay between vaginal and endometrial microbiota and offer potential interventions to enhance reproductive success in assisted reproductive technologies.

Levels of serum β-human chorionic gonadotropin after embryo transfer and subsequent miscarriage, pre-eclampsia, and intrauterine growth restriction

Background

This study aimed to examine maternal serum concentration of β-human chorionic gonadotropin (β-hCG) on Day 16 after embryo transfer and risk of miscarriage, pre-eclampsia, and intrauterine growth restriction (IUGR).

Methods

In this study, we evaluated 125 pregnancies following in vitro fertilization (IVF). β-hCG concentrations were measured on the morning of Day 16 after embryo transfer. Baseline characteristics of the study participants were also recorded.

Results

Concentrations of β-hCG on Day 16 after embryo transfer were inversely associated with the higher risk of miscarriage (p < 0.001), but did not with pre-eclampsia and IUGR (p > 0.05). Spearman's correlation coefficient showed a reverse and significant association between β-hCG and higher risk of miscarriage (σ = 0.531 and p < 0.001). There was a significant association between frozen embryo transfer and the risk of IUGR and pre-eclampsia (p = 0.005 and p = 0.023, respectively).

Conclusions

Maternal serum concentrations of β-hCG on Day 16 after IVF/embryo transfer were associated with the higher risk of miscarriage, but not pre-eclampsia and IUGR.

Pretreatment with long-acting gonadotropin-releasing hormone agonists improved pregnancy outcomes after hysteroscopic multiple polypectomies: A retrospective study of 660 frozen-thawed embryo transfer cycles

OBJECTIVE

To compare the reproductive pregnancy outcomes of pretreatment with long-acting gonadotropin-releasing hormone agonist (GnRH-a) plus hormone replacement therapy (HRT) with HRT-only cycles, and investigate differences between single polypectomy and multiple polypectomies, and between one or two doses of GnRH-a.

MATERIALS AND METHODS

This was a retrospective cohort study on patients undergoing polypectomy who underwent frozen-thawed embryo transfer (FET) from March 2018 to May 2019. They were divided into GnRH-a pretreatment and HRT-only groups. Each group was divided into single polypectomy or multiple polypectomies (in a single hysteroscopic session) subgroups. Clinical pregnancy rate and live birth rate (LBR) were the main outcomes. The effect of GnRH-a dosage was further analysed.

RESULTS

There were 212 GnRH-a pretreatment cases (45 single and 167 multiple polyps) and 448 HRT-only cases (228 single and 220 multiple polyps). The LBR of the GnRH-a pretreatment group (53.3%) was significantly higher than the HRT group (43.3%; P = 0.016). Logistic regression analysis showed that GnRH-a pretreatment significantly affected the LBR (odds ratio, OR 1.470, 95% confidence interval, Cl 1.046-2.065; P = 0.026). In the multiple polypectomy subgroup, the LBR with GnRH-a pretreatment was higher than with HRT-only (54.5% vs 43.6%; P = 0.034). However, the LBR was not different between the respective single polypectomy subgroups (48.9% vs 43.0%; P = 0.466). For patients with multiple polyps, two GnRH-a pretreatments produced a higher LBR than a single GnRH-a pretreatment (62.7% vs 47.8%), but without significant difference (P = 0.055).

CONCLUSION

GnRH-a pretreatment improved the LBR for FET cycles after hysteroscopic multiple polypectomies, independent of dose.

Atosiban application in fresh ET cycle is effective for women undergoing repeated embryo implantation failures, especially for advanced-age obese patients

To assess the effect of atosiban in pregnancy outcomes of the fresh embryo transfer (ET), the retrospective cohort study was conducted. Six hundred and eighty-nine cases (using atosiban) and 1377 age and ET cycle-matched controls were collected from the January 2016 to May 2022 to perform the fresh IVF-ET cycle. The essential characteristics and pregnancy outcomes were analyzed. Conditional logistic regression analysis and subgroup analysis were performed. In the whole samples, atosiban had no effects in the pregnancy outcomes. Subgroup analyses suggested that atosiban could improve the clinical pregnancy in more than 3 ET cycles (OR 1.667, 95% CI 1.108-2.509, P = 0.014). Moreover, the improvement of clinical pregnancy was mainly present in the advanced-age women (age ≥ 35 years: OR 1.851, 95% CI 1.136-3.014, P = 0.013), obesity (BMI ≥ 24 kg/m2: OR 2.550, 95% CI 1.105-5.883, P = 0.028) and cleavage stage embryo (D3 embryo: OR 1.721, 95% CI 1.098-2.696, P = 0.018) among the repeated implantation failures (RIF). Atosiban could also improve the live birth for the obese women. Further, in the RIF, atosiban application was strongly recommended for the advanced-age infertility women, who also had the risk of obesity with the implantation of the cleavage stage embryo. In conclusion, atosiban could improve pregnancy outcomes for the advanced-age and obese women in RIF, especially while implanting the cleavage stage embryo in fresh ET cycle.

Simultaneous transfer of one good-quality and one poor-quality cleavage stage embryo does not improve pregnancy outcomes

Embryo quality and quantity are key factors that determine the success of IVF-ET. Yet it is still unclear if, for those patients with only one good-quality embryo in an IVF cycle, the inclusion of a poor-quality embryo increases the procedure's success rate. This is a common question for both clinicians and patients in determining their course of treatment. The purpose of this work was to answer this intriguing question in the context of prognosis of patients undergoing fresh cycles with only one good-quality and more than one poor-quality cleavage-stage embryos. To control for confounding effects, we only included patients at similar age, body mass index (BMI), level of basal follicle stimulating hormone (FSH) and endometrial thickness from January 2015 to June 2021. A propensity score-matched analysis was performed to extract the matched pairs. Then we evaluated pregnancy outcome, including the rate of clinical pregnancy, live birth, embryo implantation, early miscarriage, and ectopic pregnancy. We found that the clinical pregnancy rate (34.8 vs. 38.0%, p = 0.553), live birth rate (27.1 vs. 29.9%, p = 0.598), early miscarriage rate (18.1 vs. 9.5%, p = 0.171) and ectopic pregnancy rate (1.3 vs. 1.2%, p = 1.000) did not significantly differ between those two groups, notwithstanding significant difference of the implantation rate (34.8 vs. 21.3%, p <0.001). Our work indicates that, for prognosis patients at approximately 34 years old with only one good-quality embryo, having additional poor-quality embryos does not seem to help to improve ART success rates per intended embryo transfer. In conclusion, we found that simultaneous transfer of one good-quality and one poor-quality cleavage stage embryo does not improve pregnancy outcomes.

Clinical outcomes after fresh versus frozen embryo transfer in women with advanced reproductive age undergoing in vitro fertilization: a propensity score-matched cohort study

This retrospective cohort study aimed to compare clinical outcomes following fresh or frozen embryo transfer (FET) in women with advanced reproductive age (ARA). Women aged 35-45 years who underwent their first autologous fresh or frozen cleavage stage embryo transfer cycle in the Centre for Assisted Reproduction of Shanghai First Maternity and Infant Hospital between January 2016 and December 2020 were included. The primary outcome was live birth after the first embryo transfer of the in vitro fertilization (IVF) cycle. Multiple covariates were used for propensity score matching (PSM) and generalized estimating equations were performed to examine the independent association between FET and live birth. Of the total 1453 patients, 327 patients had FET and 1126 patients had fresh ET. After the PSM procedure, 274 patients were included in each group. The live birth rate was 24.8% in the FET group and 25.2% in the fresh ET group (OR 0.98, 95% CI: 0.67-1.44, P = 0.92). Other pregnancy, perinatal and neonatal outcomes were all comparable between the two groups. This study showed that FET did not improve live birth and other clinical outcomes as compared with fresh embryo transfer in women with ARA who underwent their first IVF cycle.

Effects of the Zishen Yutai Pill compared with placebo on pregnancy outcomes among women in a fresh embryo transfer cycle: a Post Hoc subgroup analysis of a randomized controlled trial

Objective

To assess whether the administration of Zishen Yutai Pill (ZYP) could improve the pregnancy outcomes in different subgroups of women undergoing fresh embryo transfer cycles.

Materials and methods

This is a post hoc analysis of a large scale, placebo-controlled, double blind, randomized clinical trial (RCT) regarding the use of ZYP during assisted reproductive technology (ART) treatment. The RCT was conducted at 19 in vitro fertilization (IVF) centers between April 2014 and June 2017. A total of 2265 women undergoing fresh embryo transfer cycles were randomly assigned in a 1:1 ratio to receive ZYP (n = 1131) or placebo (n = 1134). Post hoc logistic regression analyses were applied in this study to examine the between-group differences of ZYP and placebo on clinical pregnancy rate among different subgroups. Detailed analyses, both in intention-to-treat (ITT) and per-protocol population, were also conducted in specific subgroups with regards to rates of implantation, biochemical pregnancy, clinical pregnancy, live birth, pregnancy loss, as well as other neonatal indices.

Results

ZYP showed a significantly higher clinical pregnancy rates than placebo in the ITT population. Detailed subgroup analyses were conducted in subgroup in advanced maternal age (AMA, ≥ 35 years old) and overweight/obese patients (BMI > 24), due to the clinical importance and statistical results. In these subgroups, baseline characteristics were similar between two arms (all P > 0.05). Significantly elevated clinical pregnancy rates were observed in ZYP cohort (both P < 0.05) compared with the placebo group. Results also showed that ZYP treatment resulted in significantly higher rates of implantation, biochemical pregnancy in AMA or overweight/obese patients in ITT analysis (all P < 0.05).

Conclusions

The current post hoc subgroup analysis suggested that AMA and overweight/obese women could experience clinical benefits when treated with ZYP in their fresh embryo transfer cycles. The study provides references for the use of ZYP in ART practices. However, further studies in specific subgroups should be examined in more rigorous clinical trial settings.

Clinical trial registration

Chictr.org.cn, ChictrTRC-14004494.

A systematic review and meta-analysis: clinical outcomes of recurrent pregnancy failure resulting from preimplantation genetic testing for aneuploidy

Background

Preimplantation genetic testing for aneuploidy (PGT-A) is an emerging technology that aims to identify euploid embryos for transfer, reducing the risk of embryonic chromosomal abnormalities. However, the clinical benefits of PGT-A in recurrent pregnancy failure (RPF) patients, particularly in young RPF patients, remains uncertain.

Objective and rationale

This meta-analysis aimed to determine whether RPF patients undergoing PGT-A had better clinical outcomes compared to those not undergoing PGT-A, thus assessing the value of PGT-A in clinical practice.

Search methods

We systematically searched PubMed, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data, and VIP Database for Chinese Technical Periodicals (VIP) from 2002 to 2022. Thirteen published studies involving 930 RPF patients screened using PGT-A and over 1,434 RPF patients screened without PGT-A were included in this meta-analysis. Clinical outcomes were evaluated based on embryo transfers after PGT-A (n=1,015) and without PGT-A (n=1,799).

Clinical outcomes

The PGT-A group demonstrated superior clinical outcomes compared to the in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) group. The PGT-A group had a significantly higher implantation rate (IR) (RR=2.01, 95% CI: [1.73; 2.34]), clinical pregnancy rate (CPR) (RR=1.53, 95% CI: [1.36; 1.71]), ongoing pregnancy rate (OPR) (RR=1.76, 95% CI: [1.35; 2.29]), live birth rate (LBR) (RR=1.75, 95% CI: [1.51; 2.03]), and significantly lower clinical miscarriage rate (CMR) (RR=0.74, 95% CI: [0.54; 0.99]). Subgroup analysis based on patient age (under 35 years and 35 years or older) showed that both PGT-A subgroups had significantly better CPR (P<0.01) and LBR (P<0.05) values compared to the IVF/ICSI groups.

Summary

This meta-analysis demonstrates that PGT-A in RPF patients, is associated with improved clinical outcomes, including higher IR, CPR, OPR, and LBR values, and lower CMR compared to the IVF/ICSI group. These findings support the positive clinical application of PGT-A in RPF patients.

Systematic Review Registration

http://INPLASY.com, identifier INPLASY 202320118.

Exploring the Impact of Controlled Ovarian Stimulation and Non-Invasive Oocyte Assessment in ART Treatments

Invasive and noninvasive features are normally applied to select developmentally competent oocytes and embryos that can increase the take-home baby rates in assisted reproductive technology. The noninvasive approach mainly applied to determine oocyte and embryo competence has been, since the early days of IVF, the morphological evaluation of the mature cumulus-oocyte complex at the time of pickup, first polar body, zona pellucida thickness, perivitelline space and cytoplasm appearance. Morphological evaluation of oocyte quality is one of the options used to predict successful fertilization, early embryo development, uterine implantation and the capacity of an embryo to generate a healthy pregnancy to term. Thus, this paper aims to provide an analytical revision of the current literature relating to the correlation between ovarian stimulation procedures and oocyte/embryo quality. In detail, several aspects of oocyte quality such as morphological features, oocyte competence and its surrounding environment will be discussed. In addition, the main noninvasive features as well as novel approaches to biomechanical parameters of oocytes that might be correlated with the competence of embryos to produce a healthy pregnancy and live birth will be illustrated.

The association between the number of oocytes retrieved and cumulative live birth rate in different female age strata

To evaluate the association between the number of oocytes retrieved and cumulative live birth rate (CLBR) in different female age strata. 17,931 women undergoing their first IVF/ICSI-ET cycle in the Sir Run Run Shaw Hospital of Zhejiang University were grouped by age (A: ≤ 35 years; B: ≥ 36 years) as well as the number of oocytes retrieved (a: ≤ 5; b:6-9; c:10-14; d: ≥ 15). Multivariate regression analysis was performed to assess the OR of CLBR for the variable 'age' and 'number of oocytes retrieved'. The group ≥ 36 years exhibited lower cumulative pregnancy rates (CPRs) and cumulative live birth rates (CLBRs), which are proportional to the number of oocytes retrieved but opposite to increasing age. Multivariate logistic regression analysis revealed that the age and number of oocytes retrieved remain significant independent predictive factors (P < 0.001). Age and number of oocytes retrieved are two independent factors affecting the CLBR. The discrepancy of the minimum number of oocytes retrieved for patients with different ages to achieve ideal CLBR is instructive for clinical practice. The practice of controlling the stimulation dose is feasible for patients ≤ 35 years who can achieve over 60% CLBR once the number of oocytes obtained is more than 6. However, additional stimulation cycles and accumulation of embryos are necessary for elderly group especially those ≥ 38 years old who need more than 14 oocytes to obtain higher live birth rate.

Finding of the optimal preparation and timing of endometrium in frozen-thawed embryo transfer: a literature review of clinical evidence

Frozen-thawed embryo transfer (FET) has been a viable alternative to fresh embryo transfer in recent years because of the improvement in vitrification methods. Laboratory-based studies indicate that complex molecular and morphological changes in endometrium during the window of implantation after exogenous hormones with controlled ovarian stimulation may alter the interaction between the embryo and endometrium, leading to a decreased implantation potential. Based on the results obtained from randomized controlled studies, increased pregnancy rates and better perinatal outcomes have been reported following FET. Compared to fresh embryo transfer, fewer preterm deliveries, and reduced incidence of ovarian hyperstimulation syndrome were found after FETs, yet there is a trend of increased pregnancy-related hypertensive diseases in women receiving FET. Despite the increased application of FET, the search for the most optimal priming protocol for the endometrium is still undergoing. Three available FET protocols have been proposed to prepare the endometrium: i) natural cycle (true natural cycle and modified natural cycle) ii) artificial cycle (AC) or hormone replacement treatment cycle iii) mild ovarian stimulation (mild-OS) cycle. Emerging evidence suggests that the optimal timing for FET using warmed blastocyst transfer is the LH surge+6 day, hCG administration+7 day, and the progesterone administration+6 day in the true natural cycle, modified natural cycle, and AC protocol, respectively. Although still controversial, better clinical pregnancy rates and live birth rates have been reported using the natural cycle (true natural cycle/modified natural cycle) compared with the AC protocol. Additionally, a higher early pregnancy loss rate and an increased incidence of gestational hypertension have been found in FETs using the AC protocol because of the lack of a corpus luteum. Although the common clinical practice is to employ luteal phase support (LPS) in natural cycles and mild-OS cycles for FET, the requirement for LPS in these protocols remains equivocal. Recent findings obtained from RCTs do not support the routine application of endometrial receptivity testing to optimize the timing of FET. More RCTs with rigorous methodology are needed to compare different protocols to prime the endometrium for FET, focusing not only on live birth rate, but also on maternal, obstetrical, and neonatal outcomes.

The time interval between oocyte retrieval and frozen embryo transfer does not impact reproductive outcomes

RESEARCH QUESTION

Does the time interval between oocyte retrieval and frozen embryo transfer (FET) affect pregnancy outcomes after a freeze-all strategy?

DESIGN

Retrospective study including a total of 5995 patients who underwent their first FET following a freeze-all cycle between 1 January 2017 and 31 December 2020. Patients were divided into immediate (the interval between oocyte retrieval and the day of first FET ≤40 days), delayed (>40 days but ≤180 days) and overdue groups (>180 days). Pregnancy and neonatal outcomes were analysed, and multivariable regression analysis was used to study the effect of FET timing on the live birth rate (LBR) in the entire cohort and the different subgroups.

RESULTS

The LBR was significantly lower in the overdue group than in the delayed group (34.9% versus 42.8%, P = 0.002); however, after adjusting for confounding factors, the difference was not statistically significant. The immediate group had a comparable LBR (36.9%) to the other two groups in both the crude and adjusted analyses. Multivariable regression analysis showed no impact of FET timing on LBR in the whole cohort or in the subgroups according to ovarian stimulation protocol, trigger type, insemination method, reason for freezing all, FET protocol or transferred embryo stage.

CONCLUSIONS

The time interval between oocyte retrieval and FET does not impact reproductive outcomes. Unnecessary delays in FET should be avoided to shorten the time to live birth.

The Effect of Different Luteal Phase Support Applications on Clinical Pregnancy Outcomes in Frozen-Thawed Embryo Transfer

Purpose

During the frozen-thawed embryo transfer (FET) method, controlled ovarian hyperstimulation is used. At the same time, progesterone support is given for luteal phase support. In this study, we investigated the effects of various luteal phase support agents administered orally, intramuscularly (IM), and vaginally during FET on pregnancy rates.

Methods

The files of 166 patients between the ages of 21 and 44 in the Assisted Reproductive Techniques Center of Acıbadem Mehmet Ali Aydınlar University Atakent Hospital were analyzed retrospectively between 2016 and 2022. The patients' FSH, LH, E2, P4, AMH, and TSH levels were measured. The GnRH antagonist protocol was initiated on the 2nd or 3rd day of menstruation. Three types of progesterone agents were used in females with PCOS. Three different methods were applied: 50 mg/ml of IM progesterone daily, 90 mg of progesterone gel 2∗1 vaginally, and dydrogesterone acetate tb. orally 3∗1. FET was performed on women who received 21 days of treatment by thawing 5th-day embryos. B-hCG was performed on the 12th day after the transfer, and evaluations were made. The study results were evaluated as follows: for the whole study group, for those <30 years of age, for those 30-35 years of age, and for those >35 years of age.

Results

A total of 164 patients, 57 females using vaginal progesterone gel, 30 females using oral progesterone tablet, and 77 females using IM progesterone, who met the inclusion criteria, were included in the study. The pregnancy outcomes of IM progesterone application were statistically significantly higher in the entire study group and the >35 age group when compared to the vaginal progesterone gel application. It was found that the pregnancy outcomes of IM progesterone application increased statistically significantly in the <30 age group when compared to outcomes in the other groups, using vaginal progesterone gel and oral progesterone tb.

Conclusions

We found that IM progesterone application was more effective than vaginal progesterone gel application for luteal phase support. Many randomized controlled, especially live birth rate studies, are required before results can more closely approximate those for the general population.

Pregnancy Outcomes Associated with Ovarian Hyperstimulation Syndrome: A Retrospective Cohort Study of Infertile Women

Objective

To assess the relationship between ovarian hyperstimulation syndrome (OHSS) and adverse outcomes using population-based data in the United States. The hypothesis is that patients with OHSS were more likely to deliver preterm and more likely to have hypertensive disorders.

Methods

This retrospective cohort study identified 94 patients with OHSS and 183 matched referents in eight counties in Minnesota. Data were collected regarding pregnancy history, infertility treatment, and pregnancy outcomes. Using the Rochester Epidemiology Project, study subjects were identified from female patients, aged 18 to 49 years, who were diagnosed with infertility from January 2, 1995 to December 1, 2017, and had a pregnancy greater than 20 weeks' gestation. The primary outcome was preterm delivery or hypertensive disorder of pregnancy incidence in the OHSS group when compared with control patients. Chi-squared test, t test, and multivariate logistic models were used where appropriate.

Results

Patients with OHSS were more likely to deliver preterm (odds ratio, 2.14; 95% confidence interval, 1.26-3.65; P < 0.01), and their neonates were more likely to be small for gestational age (odds ratio, 4.78; 95% confidence interval, 1.61-14.19; P < 0.01). No significant differences between the groups were observed in any other outcome. Patients with OHSS are more likely to deliver preterm if they undergo fresh transfer compared with a freeze all and subsequent frozen transfer (odds ratio, 3.03, 95% confidence interval, 1.20-7.66, P = 0.02).

Conclusion

OHSS may lead to preterm birth and small-for-gestational-age neonates, which changes patient counseling and leads to arranging specialized obstetrical care for these patients with OHSS.

Construction of the machine learning-based live birth prediction models for the first in vitro fertilization pregnant women

BACKGROUND

This study was to conduct prediction models based on parameters before and after the first cycle, respectively, to predict live births in women who received fresh or frozen in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) for the first time.

METHODS

This retrospective cohort study population consisted of 1,857 women undergoing the IVF cycle from 2019 to 2021 at Huizhou Municipal Central Hospital. The data between 2019 and 2020 were completely randomly divided into a training set and a validation set (8:2). The data from 2021 was used as the testing set, and the bootstrap validation was carried out by extracting 30% of the data for 200 times on the total data set. In the training set, variables are divided into those before the first cycle and after the first cycle. Then, predictive factors before the first cycle and after the first cycle were screened. Based on the predictive factors, four supervised machine learning algorithms were respectively considered to build the predictive models: logistic regression (LR), random forest (RF), extreme gradient boosting (XGBoost), and light gradient boosting machine (LGBM). The performances of the prediction models were evaluated by the area under the receiver operator characteristic curve (AUC), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy.

RESULTS

Totally, 851 women (45.83%) had a live birth. The LGBM model showed a robust performance in predicting live birth before the first cycle, with AUC being 0.678 [95% confidence interval (CI): 0.651 to 0.706] in the training set, 0.612 (95% CI: 0.553 to 0.670) in the validation set, 0.634 (95% CI: 0.511 to 0.758) in the testing set, and 0.670 (95% CI: 0.626 to 0.715) in the bootstrap validation. The AUC value in the training set, validation set, testing set, and bootstrap of LGBM to predict live birth after the first cycle was 0.841 (95% CI: 0.821 to 0.861), 0.816 (95% CI: 0.773 to 0.859), 0.835 (95% CI: 0.743 to 0.926), and 0.839 (95% CI: 0.806 to 0.871), respectively.

CONCLUSION

The LGBM model based on the predictive factors before and after the first cycle for live birth in women showed a good predictive performance. Therefore, it may assist fertility specialists and patients to adjust the appropriate treatment strategy.

Treatment options for endometrial hypoproliferation

PURPOSE OF REVIEW

Endometrial hypoproliferation refers to the failure of the endometrium to reach optimal thickness during fresh or frozen embryo transfer cycles in women undergoing infertility treatment with in-vitro fertilization (IVF). This review discusses the treatment options for endometrial hypoproliferation.

RECENT FINDINGS

Apart from factors related to the embryo quality, ultrasonographic findings associated with the endometrium, such as endometrial thickness, endometrial pattern and subendometrial blood flow, are considered key factors associated with the outcome of assisted reproductive treatment. To date, a consensus has not been reached regarding the definition of thin endometrium, while thresholds of 6, 7 or 8 mm have been used in the literature. Strategies to increase endometrial thickness can be reviewed in three groups: endocrine approaches, vitamins & supplements, and new experimental therapeutic interventions. Some of the recently introduced experimental therapeutic interventions such as platelet-rich plasma injection, stem cell treatment and tissue bioengineering are exciting potential therapies that need to be further studied.

SUMMARY

Despite a large number of publications on the topic, diagnosing and treating endometrial hypoproliferation remains a challenge. Well designed studies are needed to establish a widely accepted endometrial thickness cut-off value below which endometrial hypoproliferation is diagnosed and to generate meaningful data that would allow an evidence-based discussion of available therapeutic options with patients.

Effect of Frozen-Thawed Embryo Transfer on the Metabolism of Children in Early Childhood

Background: As a routine procedure in assisted reproductive technology (ART), it is crucial to assess the safety of frozen and thawed embryo transfer (FET). We aimed to investigate the metabolic profile of children conceived through FET in their early childhood. Method: A total of 147 children between the age of 1.5 and 4 years old, conceived through FET or naturally conceived (NC), were recruited. A total of 89 children, 65 in the FET group and 24 in the NC group (matched with the FET group based on children’s BMI) were included in the final statistical analysis of biochemical markers and metabolomics. Results: Children conceived through FET had a lower level of fasting insulin level and HORM-IR and a higher level of fasting glucose and APOE as compared to children naturally conceived. Metabolomics showed that there were 16 small differential metabolites, mainly including amino acids, carnitines, organic acids, butyric, and secondary bile acid between two groups, which enriched in Nitrogen metabolism, Butanoate metabolism, Phenylalanine metabolism, and D-Arginine and D-ornithine metabolism pathways. Conclusion: Although the FET group had a significantly higher level of APOE and fasting glucose, it cannot yet be considered that children in the FET group had an obvious disorder of glucose and lipid metabolism. However, the potentially more active intestinal flora and lower carnitine levels of children in the FET group suggested by metabolomics are worth further exploration.

Association between endometrial blood and clinical outcome in frozen single blastocyst transfer cycles

Background: The success of embryo transfer cycle depends mainly on the quality of embryo and endometrial receptivity. Ultrasound examination is still the most widely used non-invasive evaluation method for its advantages of convenience, non-invasiveness and repeatability. Ultrasound-measured endometrial blood flow is one of the important evaluation indicators of morphology. Aims: To investigate the effect of the number of endometrial blood flow branches on pregnancy outcome of frozen-thawed embryo transfer cycles which have undergoing hormone replacement therapy (HRT-FET). Material and methods: A retrospective cohort study was performed looking at a total of 1390 HRT-FET cycles from our reproductive medicine center between January 2017 to December 2021, which transferred one blastocyst frozen on day 5 with good quality in morphology. Associations between endometrial blood flow branches and pregnancy outcomes were evaluated with multivariable linear regression analysis. Results: The number of endometrial blood flow branches was independently associated with clinical pregnancy (OR 1.10; 95% CI 1.02-1.20). After adjusting for potential confounders, the effect size (odds ratio) was 1.09 (95% CI 1.00-1.19), and the results showed that the clinical pregnancy rate and live birth rate of T2 and T3 groups were significantly higher than those in group T1 (p < 0.05). Subgroup analysis showed that a consistent association between the endometrial blood flow branches and clinical pregnancy in all subgroups. Conclusion: Our study provided evidence for the influence of endometrial blood flow on pregnancy outcomes. There may be an independent association between the number of endometrial blood flow branches and pregnancy outcomes in frozen-thawed single blastocyst transfer cycles.

Pregnancy Outcomes of Freeze-All versus Fresh Embryo Transfer in Women with Adenomyosis: A Retrospective Study

Adenomyosis has been associated with adverse fertility and pregnancy outcomes, and its impact on the outcomes of in vitro fertilization (IVF) has received much attention. It is controversial whether the freeze-all strategy is better than fresh embryo transfer (ET) in women with adenomyosis. Women with adenomyosis were enrolled in this retrospective study from January 2018 to December 2021 and were divided into two groups: freeze-all (n = 98) and fresh ET (n = 91). Data analysis showed that freeze-all ET was associated with a lower rate of premature rupture of membranes (PROM) compared with fresh ET (1.0% vs. 6.6%, p = 0.042; adjusted OR 0.17 (0.01-2.50), p = 0.194). Freeze-all ET also had a lower risk of low birth weight compared with fresh ET (1.1% vs. 7.0%, p = 0.049; adjusted OR 0.54 (0.04-7.47), p = 0.642). There was a nonsignificant trend toward a lower miscarriage rate in freeze-all ET (8.9% vs. 11.6%; p = 0.549). The live birth rate was comparable in the two groups (19.1% vs. 27.1%; p = 0.212). The freeze-all ET strategy does not improve pregnancy outcomes for all patients with adenomyosis and may be more appropriate for certain patients. Further large-scale prospective studies are needed to confirm this result.

Quality of clinical prediction models in in vitro fertilisation: Which covariates are really important to predict cumulative live birth and which models are best?

The improvement in IVF cryopreservation techniques over the last 20 years has led to an increase in elective single embryo transfer, thus reducing multiple pregnancy rates. This strategy of successive transfers of fresh followed by frozen embryos has resulted in the acceptance of using cumulative live birth over complete cycles of IVF as a critical measure of success. Clinical prediction models are a useful way of estimating the cumulative chances of success for couples tailored to their individual clinical factors, which help them prepare for and plan future treatment. In this review, we describe several models that predict cumulative live birth and recommend which should be used by couples and/or their clinicians and when they should be used. We also discuss the most relevant predictors to consider when either developing new IVF prediction models or updating existing models.

Independent value of PMOI on hCG day in predicting pregnancy outcomes in IVF/ICSI cycles

OBJECTIVES

The aim of this study was to determine whether, on the day of human chorionic gonadotropin (hCG) injection, the progesterone to number of mature oocytes index (PMOI) can be used alone or together with other parameters in a fresh embryo transfer in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycle to predict pregnancy outcome.

METHODS

This was a retrospective cohort study of all couples who underwent a clinical pregnancy and received a fresh IVE/ICSI cycle at a single large reproductive medical center between June 2019 and March 2022. The study involved a total of 1239 cycles. To analyze risk factors associated with pregnancy outcomes on the day of HCG injection, univariate and multivariate logistic regression analyses were used. The area under the curve (AUC) was determined, and PMOI and other factors were compared using receiver operating characteristic (ROC) curves.

RESULTS

The clinical pregnancy rate was significantly higher in group A (60.76%) than in the other groups (Group B: 52.92% and Group C:47.88%, respectively, p =0.0306). Univariate and multivariate logistic regression revealed that PMOI levels were significantly correlated with the probability of pregnancy outcome, independent of other risk factors. More importantly, PMOI levels independently predict the occurrence of pregnancy outcome, comparable to the model combining age. The optimal serum PMOI cutoff value for pregnancy outcome was 0.063 ug/L.

CONCLUSION

Our results suggest that PMOI levels have an independent predictive value for pregnancy outcome in fresh IVF/ICSI cycles.

Congenital anomaly and perinatal outcome following blastocyst- vs cleavage-stage embryo transfer: systematic review and network meta-analysis

OBJECTIVES

To compare the reported rate of any congenital anomaly and perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer using a pairwise meta-analysis and to evaluate the same outcomes following fresh-blastocyst, frozen-blastocyst, fresh-cleavage or frozen-cleavage embryo transfer using a network meta-analysis.

METHODS

A literature search was performed in PubMed, Scopus and CENTRAL and registers for ongoing studies, from inception to February 2022, for randomized controlled trials (RCTs) with any sample size and observational studies including at least 100 live births per group, comparing the rates of any congenital anomaly and perinatal outcome of pregnancy following fresh/frozen embryo transfer at cleavage (day 2-3) vs blastocyst (day 5-7) stage. Risk ratios (RRs) along with their 95% CIs were pooled via a random-effects model meta-analysis. Within a frequentist network meta-analysis framework, outcomes of all four treatment modalities (i.e. fresh-blastocyst, fresh-cleavage, frozen-blastocyst, frozen-cleavage) were compared further. Any congenital anomaly constituted the primary outcome, whereas preterm delivery (delivery < 37 weeks), low birth weight (LBW; < 2500 g), gender of the neonate (male), perinatal death and healthy neonate (defined as liveborn neonate, delivered at term, weighing ≥ 2500 g, surviving for at least 28 days postbirth and without any congenital anomaly) were considered as secondary outcomes. Subgroup analyses by plurality (liveborn singleton vs multiple pregnancy) were conducted in the pairwise and network meta-analyses. The risk of bias was assessed using the RoB2 tool for RCTs and the ROBINS-I tool for non-randomized studies. Certainty of evidence was assessed using GRADE.

RESULTS

Through the literature search, 550 studies were retrieved and 33 were included in the systematic review. We found no significant difference in the risk for any congenital anomaly between blastocyst- and cleavage-stage transfer (RR, 0.80 (95% CI, 0.63-1.03); 10 studies; n = 192 442; I²  = 85.5%). An increased probability of a male neonate was observed following blastocyst- vs cleavage-stage transfer (RR, 1.07 (95% CI, 1.06-1.09); 18 studies; n = 227 530; I²  = 32.7%). No significant differences in other secondary outcomes or significant subgroup differences between liveborn singletons and multiple pregnancies were observed. The network meta-analysis showed a significantly lower risk for LBW following frozen-blastocyst vs fresh-blastocyst (RR, 0.76 (95% CI, 0.60-0.95)) or fresh-cleavage (RR, 0.74 (95% CI, 0.59-0.93)) transfer. Frozen-blastocyst transfer was associated with an increased risk for perinatal death compared with the fresh-cleavage method (RR, 2.06 (95% CI, 1.10-3.88)). The higher probability of a male neonate following blastocyst transfer remained evident in the network comparisons. All outcomes were assessed to be of very-low certainty of evidence.

CONCLUSIONS

Current very-low certainty of evidence shows that there may be little-to-no difference in the risk for congenital anomaly or adverse perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer, although there was a slightly increased probability of a male neonate following blastocyst transfer. When considering cryopreservation, frozen-blastocyst transfer was associated with a reduction in the risk for LBW compared with both fresh-transfer modalities, and fresh-cleavage transfer may be associated with a reduction in the risk for perinatal death compared with frozen-blastocyst transfer. High-quality RCTs with separate data on fresh and frozen cycles and consistent reporting of culture conditions and freezing methods are mandatory. Individual participant data meta-analyses are required to address the substantial inconsistency resulting from current aggregate data approaches. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Impact of progesterone-free luteal phase support following natural cycle frozen embryo transfer: Study protocol for a multicenter, non-inferiority, randomized controlled trial

Introduction

Nowadays, frozen-thawed embryo transfer (FET) has become one of the standard treatments for infertility in the field of assisted reproductive technology (ART). Natural cycle FET (NC-FET) has many advantages, such as simplicity and economics, no effect on patients’ menstrual cycles, estrogen and progesterone levels, as well as no interference in endometrial growth and transformation, which is aligned with the natural physiological state of embryo implantation. Nonetheless, there is a controversy regarding the need for luteal phase support (LPS) during NC-FET cycles. The purpose of this study is to assess whether LPS was not inferior to non-LPS in terms of OPR in NC-FET cycles.

Methods and analysis

This study including 1,010 ovulatory women undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles with an elective freeze-all strategy followed by NC-FET will be performed at four university-affiliated reproductive centers. Participants will be randomly assigned in a 1:1 ratio to receive LPS treatment or not. This study is designed as an open-label, non-inferiority, randomized controlled trial (RCT), and the primary statistical strategies were intention-to-treat (ITT) and per-protocol (PP) analysis.

Discussion

There may not have been any significant difference in the chance of a live birth after FET if no progesterone was supplemental during the luteal phase. However, due to the limited number of previous studies, which are mainly retrospective, evidence is still limited. Thus, by conducting this multicenter RCT, we intend to evaluate whether LPS is necessary in NC-FET.

Ethics and dissemination

A Reproductive Ethics Committee of the Affiliated Hospital of Shandong University of Traditional Chinese Medicine (SDUTCM) has approved this study. This study will handle the data as required by general data protection regulations. Participants will sign a written informed consent regarding participation in the study and storage of blood samples in a biobank for future research. This study will be monitored by study personnel trained in Good Clinical Practice who are not involved in the study. The results of this study will be disseminated through publication in international peer-reviewed scientific journals.

Clinical trial registration

[https://www.chictr.org.cn/], identifier [ChiCTR2200057498].

The use of frozen embryos and frozen sperm have complementary IVF outcomes: a retrospective analysis in couples experiencing IVF/Donor and IVF/Husband

Background

The cryopreservation of sperm or embryos has been an important strategy in the treatment of infertility. Recently studies have revealed the outcomes after IVF (in vitro fertilization) treatment for single-factor exposure either to frozen sperm or embryos.

Methods

This retrospective study was to uncover the exposure to both frozen sperm and embryo effects using IVF/H (in vitro fertilization using husbands’ fresh sperm) or IVF/D (in vitro fertilization using donors’ frozen sperm) treatment.

Results

The results showed the clinical pregnancy rate (CPR), live birth rate (LBR) and low birth weight rate (LBW) increased to 63.2% (or 68.1%), 61.1% (or 66.4%) and 15.8% (or 16.2%) after using frozen embryo transfer within Group IVF/H (or Group IVF/D). After using frozen sperm, the high-quality embryo rate (HER) increased to 52% and baby with birth defect rate (BDR) reduced to 0% in subgroup D/ET comparing to subgroup H/ET. While the fertilization rate (FER), cleavage rate (CLR), HER and multiple pregnancy rate (MUR) reduced to 75%, 71%, 45% and 9.2% in subgroup D/FET comparing to subgroup H/FET. Finally, our study found accumulative frozen gamete effects, including both sperm and embryos, led to the significantly increasing in the HER (p < 0.05), CPR (p < 0.001), LBR (p < 0.001) and LBW (p < 0.05) in subgroup D/FET comparing to subgroup H/ET.

Conclusion

The use of frozen embryos and frozen sperm have complementary IVF outcomes. Our findings highlighted the parent’s distinguished frozen effect not only for clinical studies but also for basic research on the mechanism of cellular response adaptations to cryopreservation.

The impact of different endometrial preparation protocols on obstetric and neonatal complications in frozen-thawed embryo transfer: a retrospective cohort study of 3,458 singleton deliveries

BACKGROUND

Frozen-thawed embryo transfer (FET) is thought to be associated with obstetric and neonatal complications after in vitro fertilization/intracytoplasmic single sperm injection (IVF/ICSI) treatment. The study aimed to determine whether the endometrial preparation protocol is an influencing factor for these complications.

METHODS

We conducted a retrospective cohort study of 3,458 women who had singleton deliveries after IVF/ICSI-FET treatment at the Centre for Reproductive Medicine of Shanghai First Maternity and Infant Hospital between July 2016 and April 2021. The women were divided into three groups according to the endometrial preparation protocols: 2,029 women with programmed cycles, 959 with natural cycles, and 470 with minimal ovarian stimulation cycles. The primary outcomes were the incidence rates of obstetric and neonatal complications, namely, hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), intrahepatic cholestasis of pregnancy (ICP), placenta previa, preterm rupture of membranes (PROM), preterm delivery, postpartum haemorrhage, large for gestational age (LGA), small for gestational age (SGA), and macrosomia.

RESULTS

After adjustments for confounding variables by multivariate logistic regression analysis, the results showed that programmed cycles had an increased risk of HDP (aOR = 1.743; 95% CI, 1.110-2.735; P = 0.016) and LGA (aOR = 1.269; 95% CI, 1.011-1.592; P = 0.040) compared with natural cycles. Moreover, programmed cycles also increased the risk of LGA (aOR = 1.459; 95% CI, 1.083-1.965; P = 0.013) but reduced the risk of SGA (aOR = 0.529; 95% CI, 0.348-0.805; P = 0.003) compared with minimal ovarian stimulation cycles. There were no significant differences between natural cycles and minimal ovarian stimulation cycles.

CONCLUSIONS

During IVF/ICSI-FET treatment, the risk of HDP and LGA was increased in women with programmed cycles. Therefore, for patients with thin endometrium, irregular menstruation or no spontaneous ovulation, minimal ovarian stimulation cycles may be a relatively safer option than programmed cycles.

Incidence and risk factors for early pregnancy loss in women with first pregnancy undergoing in vitro fertilization-embryo transfer

Background

This study aimed to explore the incidence and influencing factors for early pregnancy loss (EPL) in infertility patients with first pregnancy undergoing in vitro fertilization (IVF) embryo transfer cycles in Jilin province, China.

Methods

A retrospective study of 2709 first pregnancy embryo transfer cycles collected from January 2016 to January 2021 was performed. The cycles were divided into the EPL group (n = 411) and the live birth group (n = 2298) according to the cycle outcomes.

Results

The EPL rate of the first-time pregnancies for infertility patients undergoing fresh/frozen-thaw embryo transfer cycle was 14.1%. Female patients aged 40 and older had increased odds of EPL compared to those under 35 (OR = 3.97, 95%CI: 2.80–7.55). Female patients with a body mass index (BMI) of 25 or greater were more likely to have EPLs than those in the normal BMI range (OR = 1.32, 95%CI: 1.03–1.70). The odds of EPL after frozen-thaw embryo transfer were higher than those after fresh embryo transfer (OR = 1.59, 95%CI: 1.11–2.27). A thin endometrium on the day of embryo transfer increased the odds of EPL (OR = 1.84, 95%CI: 1.01–3.33). Transferring more than two embryos had lower odds of EPL than single-embryo transfer (OR = 0.67, 95%CI: 0.50–0.90). Compared with other infertility diagnoses, tubal factor alone was associated with lower odds of EPL (OR = 0.72, 95%CI: 0.53–0.98).

Conclusions

The risk factors for EPL were age 40 and older, obesity, frozen-thaw cycle, thin endometrium, and non-isolated tubal factor.

Embryo cryopreservation leads to sex-specific DNA methylation perturbations in both human and mouse placentas

In vitro fertilization (IVF) is associated with DNA methylation abnormalities and a higher incidence of adverse pregnancy outcomes. However, which exposure(s), among the many IVF interventions, contributes to these outcomes remains unknown. Frozen embryo transfer (ET) is increasingly utilized as an alternative to fresh ET, but reports suggest a higher incidence of pre-eclampsia and large for gestational age infants. This study examines DNA methylation in human placentas using the 850K Infinium MethylationEPIC BeadChip array obtained after 65 programmed frozen ET cycles, 82 fresh ET cycles and 45 unassisted conceptions. Nine patients provided placentas following frozen and fresh ET from consecutive pregnancies for a paired subgroup analysis. In parallel, eight mouse placentas from fresh and frozen ET were analyzed using the Infinium Mouse Methylation BeadChip array. Human and mouse placentas were significantly hypermethylated after frozen ET compared with fresh. Paired analysis showed similar trends. Sex-specific analysis revealed that these changes were driven by male placentas in humans and mice. Frozen and fresh ET placentas were significantly different from controls, with frozen samples hypermethylated compared with controls driven by males and fresh samples being hypomethylated compared with controls, driven by females. Sexually dimorphic epigenetic changes could indicate differential susceptibility to IVF-associated perturbations, which highlights the importance of sex-specific evaluation of adverse outcomes. Similarities between changes in mice and humans underscore the suitability of the mouse model in evaluating how IVF impacts the epigenetic landscape, which is valuable given limited access to human tissue and the ability to isolate specific interventions in mice.

Influences of fresh and frozen embryo transfer on neonatal birthweight and the expression of imprinted genes PEG10 /L3MBTL1 in placenta

To investigate the influences of fresh embryo transfer (ET) and frozen embryo transfer (FET) on neonatal birthweight and the expression of imprinted genes PEG10 and L3MBTL1 in the placenta after in vitro fertilization-embryo transfer (IVF-ET), we analyzed the neonatal birthweight between fresh ET and FET transfer cycles. Then, we collected placentas delivered by fresh ET and FET, and real-time quantitative PCR, Western blotting and immunohistochemistry were used to detect the expression of PEG10 and L3MBTL1. The mean neonatal birthweight of fresh ET was lower than that of FET(3348.48 ± 521.05 vs. 3450.34 ± 524.13, P < 0.001). The risks of low birthweight (LBW) and small-for-gestational age (SGA) were lower after FET (3.9 % vs. 5.4 %; 7.2 % vs. 10.3 %), with adjusted rate ratios of 0.74 (95 % CI, 0.59-0.93; P = 0.003) and 0.70 (95 % CI, 0.59-0.84; P < 0.001), respectively. FET resulted in higher frequencies of macrosomia and large-for-gestational age (LGA) (14.2 % vs. 10.3; 11.0 % vs. 7.1 %) than fresh ET, with adjusted rate ratios of 1.45 (95 % CI, 1.26-1.68; P < 0.001) and 1.62 (95 % CI, 1.37-1.91; P < 0.001), respectively. We also observed PEG10 mRNA and protein expression levels in placentas delivered by fresh ET and FET were significantly different, but there were no significant differences in L3MBTL1 between the two groups. Fresh ET may affect the expression of the imprinted gene PEG10 in the placenta and adverse to placental implantation and development, resulting to increasing incidences of LBW and SGA.

Extended culture of cleavage embryo to blastocyst embryo is among the good predictors of successful outcome in vitrified-thawed ICSI cycles

Background

Previous studies showed that top-quality embryo transfer (ET), number of transferred embryos, endometrial preparation with natural cycles or mild stimulation, and female BMI independently affected the outcome in frozen-thawed ET. However, the effect of culturing thawed cleavage embryos to blastocyst stage on the outcome was not sufficiently elucidated. Our objective is to evaluate the role of this extended culturing as predictor of cycle outcome in vitrified-thawed ICSI cycles.

Materials and methods

One thousand forty-two consecutive cycles of vitrified-thawed ET done in a single IVF unit [Mansoura Integrated Fertility Centre (MIFC)] were reviewed during a period from 2014 to 2017. Endometrial preparation methods were natural, stimulation by antiestrogen and/or gonadotropins, or replacement using sequential estradiol (E2) and progesterone (P4). The primary outcome was the clinical pregnancy rate while the secondary outcome was the chemical and ongoing pregnancy rate.

Results

Overall clinical pregnancy rate (CPR) is 298/1042 is 28.5%, chemical pregnancy rate (326/1042) 31.3%, and ongoing pregnancy rate (167/615) 27.2%. Comparing clinically pregnant (n = 298) and non-pregnant (n = 744) showed, respectively, the following: age 28.76 ± 5.0, 28.85 ± 5.18 (p = 0.8); BMI 31.06 ± 5.9, 32.45 ± 5.9 (p = 0.002); infertility duration 4.17 ± 3.2, 4.6 ± 3.5 (p = 0.038); endometrial thickness 10.82 ± 1.6, 10.13 ± 2.06 (p = 0.0001); and no. of ET 3.35 ± 1.5, 3.12 ± 1.60 (p = 0.035). The clinical pregnancy rate when vitrification was done on cleavage embryos was 198/502 (39.4%), and when vitrification done on blastocyst stage 100/ 536 (18.7%) (P < 0.0001); endometrial preparation: natural 72/240(29.1%), stimulated 204/680 (30.0%) replacement 17/90 (18.8%) (p = 0.09); extended culture of cleavage embryos to blastocyst stage: clinical pregnancy rate 116/194 (59.7%) chemical pregnancy rate 125/194 (64.1%), ongoing pregnancy rate 87/165 (52.7%) and non extended culture clinical pregnancy rate 182/848 (21.4%), chemical pregnancy rate 201/848 (23.7%), and ongoing pregnancy rate 80/450 (17.7%) (P < 0.0001).

Conclusion

Top-quality ET, number of transferred embryos and extended culture of cleavage embryos to blastocyst stage, cleavage embryos but not infertility duration, BMI, endometrial thickness, or hCG trigger of ovulation independently predict successful outcome in frozen cycle ET and extended culture of cleavage embryos significantly improved clinical and chemical and ongoing pregnancy rates.

Predicting the probability of a live birth after a freeze-all based in vitro fertilization-embryo transfer (IVF-ET) treatment strategy

BACKGROUND

The predictors for live birth rate (LBR) following one episode of in vitro fertilization (IVF) cycle for patients using a "freeze-all" strategy are not entirely clear.

METHODS

A retrospective cohort study utilizing a prediction model was developed to assess the relationship to the LBR. Women undergoing IVF with a freeze-all strategy were screened. Univariate models were first fitted for female age at oocytes retrieval/frozen-thawed embryo transfer (FET), body mass index (BMI), duration and etiology of infertility, previous IVF failures, total dose and duration of gonadotrophin, ovarian sensitivity index (OSI), number of oocytes collected, method of fertilization, number of embryos created, number and stage of embryos frozen, type and number of FET cycles, endometrial thickness (EMT)/pattern, hormone level on transplantation day, storage duration, number of embryos thawed and damaged thawed embryos, number and stage of embryos transferred and number of different quality embryos transferred. Variables with P<0.05 in the univariate model were selected for further analysis of the final multivariate discrete-time logistic regression model.

RESULTS

A total of 7,602 women undergoing one ovarian stimulation resulted in 9,964 FETs, of whom 3,066 (40.33%) had a live-birth after their first FET and 3,929 (51.68%) after total FETs. The EMT and woman's age at oocyte retrieval were the most important predictors. In the first FET, the LBR of women with an EMT ≤8 mm [27.40%; 95% confidence interval (CI): (21.60-33.81%)] was significantly lower than that of women with EMT between 9 and 11 mm [36.51%; 95% CI: (34.25-38.81%)] and thicker than 12 mm [44.23%; 95% CI: (42.22-46.25%)] (P<0.05). The optimistic and conservative cumulative LBRs of women younger than 31 years [87.5%; 95% CI: (86.32-88.61%) and 63.04%; 95% CI: (61.36-64.69%)] were significantly decreased in women aged 31-35, 36-40 and >40 (P<0.001).

CONCLUSIONS

Our study provides an effective prediction model for a woman's chance of having a baby after a "freeze-all" policy. The use of EMT and female age as tools to identify LBR are shown to be justified, and repeated FETs cannot reverse the age-dependent decline in fertility.

Transfer of thawed frozen embryo versus fresh embryo to improve the healthy baby rate in women undergoing IVF: the E-Freeze RCT

BACKGROUND

Freezing all embryos, followed by thawing and transferring them into the uterine cavity at a later stage (freeze-all), instead of fresh-embryo transfer may lead to improved pregnancy rates and fewer complications during in vitro fertilisation and pregnancies resulting from it.

OBJECTIVE

We aimed to evaluate if a policy of freeze-all results in a higher healthy baby rate than the current policy of transferring fresh embryos.

DESIGN

This was a pragmatic, multicentre, two-arm, parallel-group, non-blinded, randomised controlled trial.

SETTING

Eighteen in vitro fertilisation clinics across the UK participated from February 2016 to April 2019.

PARTICIPANTS

Couples undergoing their first, second or third cycle of in vitro fertilisation treatment in which the female partner was aged < 42 years.

INTERVENTIONS

If at least three good-quality embryos were present on day 3 of embryo development, couples were randomly allocated to either freeze-all (intervention) or fresh-embryo transfer (control).

OUTCOMES

The primary outcome was a healthy baby, defined as a live, singleton baby born at term, with an appropriate weight for their gestation. Secondary outcomes included ovarian hyperstimulation, live birth and clinical pregnancy rates, complications of pregnancy and childbirth, health economic outcome, and State-Trait Anxiety Inventory scores.

RESULTS

A total of 1578 couples were consented and 619 couples were randomised. Most non-randomisations were because of the non-availability of at least three good-quality embryos (n = 476). Of the couples randomised, 117 (19%) did not adhere to the allocated intervention. The rate of non-adherence was higher in the freeze-all arm, with the leading reason being patient choice. The intention-to-treat analysis showed a healthy baby rate of 20.3% in the freeze-all arm and 24.4% in the fresh-embryo transfer arm (risk ratio 0.84, 95% confidence interval 0.62 to 1.15). Similar results were obtained using complier-average causal effect analysis (risk ratio 0.77, 95% confidence interval 0.44 to 1.10), per-protocol analysis (risk ratio 0.87, 95% confidence interval 0.59 to 1.26) and as-treated analysis (risk ratio 0.91, 95% confidence interval 0.64 to 1.29). The risk of ovarian hyperstimulation was 3.6% in the freeze-all arm and 8.1% in the fresh-embryo transfer arm (risk ratio 0.44, 99% confidence interval 0.15 to 1.30). There were no statistically significant differences between the freeze-all and the fresh-embryo transfer arms in the live birth rates (28.3% vs. 34.3%; risk ratio 0.83, 99% confidence interval 0.65 to 1.06) and clinical pregnancy rates (33.9% vs. 40.1%; risk ratio 0.85, 99% confidence interval 0.65 to 1.11). There was no statistically significant difference in anxiety scores for male participants (mean difference 0.1, 99% confidence interval -2.4 to 2.6) and female participants (mean difference 0.0, 99% confidence interval -2.2 to 2.2) between the arms. The economic analysis showed that freeze-all had a low probability of being cost-effective in terms of the incremental cost per healthy baby and incremental cost per live birth.

LIMITATIONS

We were unable to reach the original planned sample size of 1086 and the rate of non-adherence to the allocated intervention was much higher than expected.

CONCLUSION

When efficacy, safety and costs are considered, freeze-all is not better than fresh-embryo transfer.

TRIAL REGISTRATION

This trial is registered as ISRCTN61225414.

FUNDING

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 25. See the NIHR Journals Library website for further project information.

Comparison of two endometrial preparation methods for frozen-thawed embryo transfer in anovulatory PCOS patients: impact on miscarriage rate

OBJECTIVE

- Some studies have suggested that patients with polycystic ovary syndrome (PCOS) are at high risk of miscarriage. However, this still remains controversial. Several potential factors might explain this association: obesity, hyperinsulinemia and hyperandrogenism. Artificial and stimulated cycles appear to be comparable for endometrial preparation in frozen-thawed embryo transfer (FET) in PCOS patients. Only a few studies have assessed miscarriage rates specifically in PCOS. We have evaluated the impact of endometrial preparation on FET outcomes in anovulatory PCOS patients.

METHODS

- A retrospective cohort study was conducted at the Lille University Hospital, including 255 FET cycles in 134 PCOS patients between January 2011 and December 2017. PCOS was defined by the presence of at least two of the three Rotterdam's criteria. Patients were under 35 years old. Two endometrial preparation protocol were studied: stimulated cycle (gonadotropins on the second day of the cycle and luteal phase support including natural progesterone 600 mg/day) and artificial cycle (6 mg oral estradiol valerate and 800 mg micronized vaginal progesterone daily).

RESULTS

- 137 FET were performed under stimulated cycle and 118 FET under artificial cycle. Early pregnancy rates (30% versus 37.3%, p = NS), miscarriage rates (22% versus 25%, p = NS) and live birth rates (23.4% versus 26.3%, p = NS) were similar.

CONCLUSIONS

- In anovulatory PCOS women, the type of endometrial preparation does not influence FET outcomes, specifically regarding the miscarriage rate.

Towards an Improved Understanding of the Effects of Elevated Progesterone Levels on Human Endometrial Receptivity and Oocyte/Embryo Quality during Assisted Reproductive Technologies

Ovarian stimulation is an indispensable part of IVF and is employed to produce multiple ovarian follicles. In women who undergo ovarian stimulation with gonadotropins, supraphysiological levels of estradiol, as well as a premature rise in progesterone levels, can be seen on the day of hCG administration. These alterations in hormone levels are associated with reduced embryo implantation and pregnancy rates in IVF cycles with a fresh embryo transfer. This article aims to improve the reader’s understanding of the effects of elevated progesterone levels on human endometrial receptivity and oocyte/embryo quality. Based on current clinical data, it appears that the premature rise in progesterone levels exerts minimal or no effects on oocyte/embryo quality, while advancing the histological development of the secretory endometrium and displacing the window of implantation. These clinical findings strongly suggest that reduced implantation and pregnancy rates are the result of a negatively affected endometrium rather than poor oocyte/embryo quality. Understanding the potential negative impact of elevated progesterone levels on the endometrium is crucial to improving implantation rates following a fresh embryo transfer. Clinical studies conducted over the past three decades, many of which have been reviewed here, have greatly advanced our knowledge in this important area.

Embryonic Development in Relation to Maternal Obesity Does Not Affect Pregnancy Outcomes in FET Cycles

This retrospective cohort study examined the effect of maternal BMI on embryo morphokinetics using a time-lapse incubator (TLI) and evaluated the effect on outcomes of frozen embryo transfer (FET) cycles. The study included 641 women who underwent FET of a total of 2553 embryos from January 2017 to August 2019. The women were divided into four groups according to BMI: underweight (<18.5 kg/m2), normal weight (18.5−24.99 kg/m2), overweight (25.0−29.99 kg/m2), and obese (≥30 kg/m2). Embryos were transferred on day 3 or 5, and their development was monitored using a TLI. We found that oocytes from obese patients were slower in the extraction of the second polar body (tPB2) after fertilization and the two pronucleus stage appeared later compared to normal-weight women. The time to fading of the pronucleus (tPNf), t2, and t4 were comparable between the four groups. Oocytes from underweight and overweight women had significantly faster cleavage at t3 and t5−t8 compared to normal weight. We did not find any significant difference in pregnancy rate, clinical pregnancy rate, or miscarriage rate among groups. In conclusion, embryos from normal-weight patients had slower cleavage rates compared to obese patients, while embryo quality was similar between BMI groups. The cycle outcomes demonstrated comparable pregnancy rates among the BMI groups.

Ovarian Stimulation in Assisted Reproductive Technology Cycles for Varied Patient Profiles: An Indian Perspective

Controlled ovarian stimulation has been an integral part of in vitro fertilisation (IVF) treatment cycles. Availability of different gonadotropins for ovarian stimulation and gonadotropin releasing hormone (GnRH) analogues for prevention of premature rise of leutinising hormone during follicular phase offer an opportunity to utilise them for a successful outcome in women with different subsets of ovarian response. Further, use of GnRH agonist as an alternative for human chorionic gonadotropin improves safety of ovarian stimulation in hyper-responders. Mild ovarian stimulation protocols have emerged as an alternative to conventional protocols in the recent years. Individualisation plays an important role in improving safety of IVF in hyper-responders while efforts continue to improve efficacy in poor responders. Some of the follicular and peri-ovulatory phase interventions may be associated with negative impact on the luteal phase and segmentalisation of the treatment with frozen embryo transfer may be an effective strategy in such a clinical scenario. This narrative review looks at the available evidence on various aspects of ovarian stimulation strategies and their consequences. In addition, it provides a concise summary of the evidence that has emerged from India on various aspects of ovarian stimulation.

Does Post-Warming Extended Culture Duration Affect the Clinical and Obstetric Outcomes of Patients of Advanced Maternal Age? A Single-Center Study

BACKGROUND

The single vitrified-warmed blastocyst transfer (SVBT) cycle has been increasingly utilized for assisted reproductive technology. Women of advanced maternal age (AMA) comprise a significant portion of patients who have undergone 'freeze-all' cycles. This study investigated the association between the post-warming extended culture duration and pregnancy outcomes in patients of AMA.

METHODS

This retrospective cohort study analyzed the outcomes of 697 SVBT cycles between January 2016 and December 2017. The cycles were divided into 3 groups based on the age of the female partners: group I: < 35 years (n = 407), group II: 35-37 years (n = 176); and group III, 38-40 years (n = 114). Data are shown as the mean ± standard error of the mean. Data were analyzed using one-way ANOVA followed by Duncan's multiple range test. Statistical significance was set at P < 0.001.

RESULTS

The blastocyst rate, clinical pregnancy rate, and live birth rate (LBR) was significantly lower in the AMA groups. However, there were no significant differences in LBR in the transfer between the AMA and younger groups according to blastocyst morphology and post-warming extended culture duration.

CONCLUSION

Post-warming extended culture of blastocysts is not harmful to patients of AMA. It could be a useful parameter in clinical counseling and decision making for fertility treatments.

Short (seven days) versus standard (fourteen days) oestrogen administration in a programmed frozen embryo transfer cycle: a retrospective cohort study

Research question

What influence does seven days of oestrogen administration versus fourteen days have on the reproductive outcomes of frozen-thawed embryo transfer (FET) in programmed endometrial preparation cycles?

Design

In a retrospective study, conducted at a university-affiliated tertiary hospital, a total of 2628 infertile patients (4142 FET cycles) were divided into one of two groups between January 2014 and December 2020: group A (n = 1406, seven days of oestrogen before progesterone (P4) supplementation) and group B (n = 2716, fourteen days of oestrogen before P4 supplementation). The primary outcome was cumulative live birth rate (CLBR). Secondary outcomes were other pregnancy-related outcomes, maternal and neonatal complications.

Results

No significant difference in CLBR was observed when comparing seven versus fourteen days of oestrogen administration before starting P4 supplementation (47.6% vs. 48.8%, P = 0.537). Furthermore, multivariable logistic regression analysis revealed that oestrogen administration in programmed FET cycles (7 days vs. 14 days) was not significantly associated with CLBR (OR 1.04, 95% CI 0.89–1.23). The risks of maternal and neonatal complications were comparable between the two groups.

Conclusions

Variation in the duration of oestradiol supplementation before P4 initiation does not impact FET reproductive outcomes. For infertile women who desire to conceive as soon as feasible, short (seven days) oestrogen administration in a programmed FET cycle may be a suitable alternative.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-022-00967-5.

Wisdom of Freezing All Valuable Embryos

Background: It is controversial whether that “Freeze-only” strategy is superior to Fresh embryo transfer in ART patients with normal ovarian response. There are two reasons supporting a “Freeze-only” strategy. One is that frozen-thawed embryos are transferred to a more physiologically receptive endometrium. While fresh embryos are transferred to a badly affected one because of controlled-ovarian stimulations, which cause the discordant development of the endometrium, when thawed-frozen embryos are transferred in a subsequent cycle the endometrium is not affected by high estrogen levels. The other reason is the big difference in cryopreservation and stimulation techniques.

Methods: We investigated the annual ART reports in Japan from 1992 to 2018, and our clinical outcomes of frozen-thawed embryo transfers and fresh embryo transfers from 2015 to 2019. This enabled the assessment of the survival rate of frozen blastocyst by Cryotop safety kit after thawing in four different clinics. We compared the outcomes of frozen embryo transfer (FroET) to fresh embryo transfer.

Results: The proportion of birth in Japan in the study interval found that FroET was responsible for 86.7% of births, compared to 13.3% of births resulting from fresh embryo transfers after IVF or intracytoplasmic sperm injection (ICSI). Clinical outcome of FroET in our clinic was significantly higher than that of fresh embryo transfer regardless of maternal age and number of collected oocytes. Average survival rate of frozen blastocyst by Cryotop safety kit after thawing in four clinics was over 95%.

Conclusions: We believe that “Freeze-only high-quality blastocysts” is superior to fresh embryo transfer in terms of clinical outcome, at least when compared to historical results.

Optimal individualization of patient-oriented ovarian stimulation in Japanese assisted reproductive technology clinics, a review for unique setting with advanced-age patients

Ovarian stimulation is a key issue in assisted reproductive technology (ART) treatment. ART practice in Japan is unique with various types of ovarian stimulation protocols, which may contribute to lower pregnancy rates compared to other countries. This review aims to clarify optimal individualized ovarian stimulation for improving the pregnancy rate per one oocyte retrieval cycle in Japan. We performed a literature review to describe ovarian stimulation, classification of infertile women depending on ovarian reserve and response, and Japanese ART data and discussed optimal conventional and mild ovarian stimulation protocols in Japan. According to Japanese ART registry data, the live birth rate of 30-35-year-old women was 32%-37% per ET cycle; therefore, four to five embryos are calculatedly needed when aiming a cumulative live birth rate of ≥80%. Mild stimulation aimed at collecting 5-10 oocytes can be alternative choice as an optimal ovarian stimulation protocol in young women. In 40-year-old women, the live birth rate is 18.8%, resulting in eight or more embryos as necessary. Conventional stimulation must be required in women with advanced age. In poor responders, however, mild stimulation may be sufficient for maximumly extracting their ovarian function. In Japan, mild ovarian stimulation can be selected in patients with a good prognosis and poor responders; however, conventional ovarian stimulation is necessary for women in advanced age.

Plane of nutrition and FSH-induced superovulation affect the expression of steroid hormone receptors and growth factors in caruncular tissue of non-pregnant sheep

Implantation is a critical step in the establishment of pregnancy and an important part of embryo-maternal contact. Uterine receptivity can be affected by changes in body condition and the maternal endocrine milieu, including those caused by the use of exogenous gonadotropins in controlled ovarian hyperstimulation to induce the development of multiple follicles. This study demonstrates the effects of FSH-mediated ovarian hyperstimulation on the caruncles of ewes under various feeding regimes. Sheep were classified into 3 categories: control fed (CF), overfed (OF), or underfed (UF). In each group, animals were superovulated with FSH or injected with a saline solution (non-treated control). Uterine caruncles were collected at the early (d 5) and mid-luteal phase (d 10) of the estrous cycle. The transcript levels of steroid hormone receptors (ESR1, ESR2, PGR) and growth factors (IGF1, IGF2, VEGFA) were investigated and their expression localized by immunohistochemical staining. As for the main findings, day of the estrous cycle affected expression of ESR1, IGF1 and IGF2, but not of ESR2, PGR and VEGFA; both feeding and superovulation had modulatory effects, with feeding (UF/OF) stimulating expression of all genes studied, and superovulation altering expression of some genes, eg IGF1, PGR and ESR1 and ESR2, in CF animals. Similarly, feeding (UF/OF) altered responsiveness to superovulation for PGR on d 5 and ESR1/ESR2 on d 5 and/or 10. Our data emphasize possible effects of dietary and/or hormonal stimuli on uterine physiology, which may affect pregnancy outcomes by disrupting uterine functionality.

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.

Pregnancy outcome of freeze thaw cycles of polycystic ovary syndrome patients regarding the anti-Müllerian hormone percentile

Patients with polycystic ovary syndrome display increased levels of anti-Müllerian hormone. Frozen-thawed embryo transfer (FET) prevents ovarian hyperstimulation and results in better pregnancy outcome in PCOS patients. Therefore, we aimed to evaluate the effect of serum AMH levels on the pregnancy outcome of FET cycles in PCOS patients. 110 infertile women with PCOS who were recommended for embryo cryopreservation followed by FET. The patients' AMH levels were evaluated, and the age-related AMH percentiles were determined. The patients were then grouped according to AMH percentiles, namely, 75th-90th percentile (Group 1) and higher than the 90th percentile (Group 2).A total of 110 PCOS patients who conceived in Frozen Embryo Transfer (FET)-In-vitro Fertilisation (IVF) cycles were included in this study. The preterm delivery rates in FET cycles were higher in the group of PCOS patients with AMH levels greater than the 90th percentile than in patients in the 75th-90th percentile group (50% vs 28.8%, p = .024). In conclusion, PCOS patients with AMH levels higher than the 90^th percentile had substantially higher preterm delivery rates than those with AMH levels at the 75^th-90^th percentile, suggesting the need for closer follow-up. Further studies are needed to elucidate the underlying mechanisms behind this correlation.IMPACT STATEMENTWhat is already known on this subject? The association of AMH levels with the risk of adverse pregnancy outcomes has been previously investigated. In women with PCOS, substantially elevated AMH levels were significantly associated with preterm birth.What do the results of this study add? Results showed that the PCOS patients with higher AMH levels and underwent assisted reproductive treatment demonstrated an increased risk of preterm labour than the PCOS patients with lower AMH levels.What are the implications of these findings for clinical practice and/or further research? In women with PCOS, substantially elevated AMH levels were significantly related to preterm birth, suggesting the need for closer follow-up in this population and the need for further studies to elucidate the underlying mechanisms behind this correlation.