Live birth rates with a freeze-only strategy versus fresh embryo transfer: secondary analysis of a randomized clinical trial

The prevalence of late-follicular phase progesterone elevation and impact on the ongoing pregnancy rate after fresh and frozen blastocyst transfer. Sub-study of an RCT

The effect of late-follicular phase progesterone elevation (LFPE) during ovarian stimulation on reproductive outcomes in ART treatment remains controversial, but recent studies indicate lower pregnancy rates with rising progesterone levels. This study aims to investigate the prevalence of late-follicular phase progesterone elevation (LFPE) and possible impact on ongoing pregnancy rate after fresh or frozen blastocyst transfer in a sub-study setting of a randomised controlled trial. A total of 288 women were included (n=137 and n=151 in the fresh transfer and freeze-all group, respectively). Among these 11(3.8%) had a progesterone level ≥1.5 ng/ml, and 20(6.9%) had a progesterone level ≥1.2 ng/ml on trigger day. Spline regression analysis showed no significant effect of late follicular phase progesterone levels on ongoing pregnancy. In the multivariate regression analysis (n = 312) only age, but not progesterone level on trigger day was significantly associated with ongoing pregnancy. In conclusion, in a clinical setting with moderate gonadotrophin stimulation and well-defined trigger and fresh transfer cancellation criteria, the prevalence of women with LFPE ≥1.5 ng/ml was low and did not indicate the clinical value of routine measurement of progesterone in the late follicular phase.

A critical appraisal of studies on endometrial thickness and embryo transfer outcome

A receptive endometrium is required for successful embryo implantation. Endometrial thickness, as measured by ultrasonography, is the most commonly used marker of endometrial receptivity in assisted reproductive technology cycles. Several factors simultaneously affect both endometrial thickness and probability of live birth, including age, oestradiol concentration and oocyte number, among others. Most of the studies investigating a relationship between endometrial thickness and embryo transfer outcomes are retrospective and do not adequately address confounding factors, in addition to other limitations. Despite multiple meta-analyses and studies with large numbers of cycles, controversy still exists. The difference between the results from prospective and retrospective studies is also striking. This article presents a critical appraisal of the studies on endometrial thickness and embryo transfer outcomes in order to highlight methodological issues and how they can be overcome in future studies. Currently available evidence does not seem to support a modification of management just because endometrial thickness is below an arbitrary threshold.

Association between serum LH levels on hCG trigger day and live birth rate after fresh embryo transfer with GnRH antagonist regimen in different populations

Objective

To investigate whether serum LH levels on hCG trigger day are associated with live birth rate (LBR) after fresh embryo transfer with GnRH antagonist regimen in different populations.

Methods

This study was a retrospective study. A total of 3059 fresh embryo transfers were divided into three populations: predicted normal ovarian responders (NOR) (n=2049), patients with PCOS (n=533), and predicted poor ovarian responders (POR) (n=477). Each population was stratified into three groups based on LH levels: < 25th percentile, 25-75th percentile, and > 75th percentile. The primary outcome of the study was LBR, and secondary outcomes included implantation, clinical pregnancy, and early pregnancy loss rates. Univariable and multivariable regression analyses were performed to adjust for potential confounders.

Results

In NOR, compared to the reference group (>75th percentile), LBR was significantly lower in the < 25th percentile group (adjusted OR=0.662; 95%CI, 0.508-0.863) and 25-75th percentile group (adjusted OR=0.791; 95%CI, 0.633-0.988). In PCOS patients, LBR decreased significantly in the < 25th percentile group (41.4%) compared to the 25-75th percentile group (53.7%) and > 75th percentile group (56.1%). In addition, the LBR was lower in the < 25th percentile group (33.6%) compared with the 25-75th percentile group (43.4%) and the>75th percentile group (42.0%) in POR, but this was not statistically significant.

Conclusions

High serum LH levels are associated with increased LBR after fresh embryo transfer in GnRH antagonist cycles, which may be attributable to higher implantation rate. LH may be a predictor of whether to schedule fresh embryo transfer in IVF cycles for better clinical outcomes.

IVF/ICSI Outcomes After a Freeze-All Strategy: an Observational Cohort Study

In order to inform patients undergoing ART regarding their chances for motherhood, it seems useful to describe "freeze all" outcomes according to the different potential indications. The goal of this study was to examine the impact of a "freeze-all approach" on the cumulative live birth rate (cLBR) according to the indication. It is a cohort study including women who had undergone ovarian stimulation (OS) using an antagonist protocol with GnRH agonist triggering between 09.2016 and 09.2018 followed by a freeze-all cycle of blastocyst embryos. The ART outcomes were compared between the two main indications of the freeze-all strategy which were in our cohort: risk of ovarian hyperstimulation syndrome (OHSS) and endometriosis. The ART outcomes were also described for the others indications (inadequate endometrium and/or premature progesterone elevation at trigger day, two or more previous ART failures, and autoimmune disease and/or a high risk of thromboembolic disease (AI and/or TE risk)). In total, 658 women were included. The cLBR in the total population was 37.7% (248/658). The cLBR was significantly higher in the "OHSS risk" group (133/281, 47.3%) than in the "endometriosis" group (69/190, 36.3%) (p = 0.017). No significant differences were noted regarding perinatal outcomes, except a significantly higher risk of placenta praevia (PP) observed in the "endometriosis" group (10.1%) (p = 0.002). The "freeze-all approach" yielded good results in terms of the cLBR and especially in case of OHSS risk. These data should be taken into account when informing patients about the ART strategy and their chances of motherhood.

Anti-Müllerian hormone in guiding the selection of a freeze-all versus a fresh embryo transfer strategy: a cohort study

PURPOSE

To explore an interaction effect between serum anti-Müllerian hormone (AMH) levels and the relative treatment effect of a freeze-all versus a fresh embryo transfer strategy on live birth.

METHODS

This was a retrospective cohort study investigating couples with infertility and eligible for both freeze-all and fresh embryo transfer between 2017 and 2019. Women with an absolute indication for a freeze-all strategy were excluded. Multivariable fractional polynomial interaction analysis within a logistic regression model was used to evaluate whether the treatment effect of a freeze-all versus a fresh transfer strategy varied at different AMH levels. Non-linear interactions were also considered. The primary outcome was the live birth after the first transfer.

RESULTS

A total of 13,503 women underwent a fresh embryo transfer and 2247 women underwent a freeze-all strategy. Live birth rates were slightly higher in the freeze-all group compared to those in the fresh embryo transfer group (35% vs 33%). There was a non-linear interaction between baseline serum AMH levels and the relative treatment effect of a freeze-all strategy versus a fresh transfer strategy on live birth (P = 0.0161). The benefit on live birth from a freeze-all embryo transfer strategy was greatest in women with a high serum level (> 7 ng/ml). The interaction remained valid when different imputation methods were used.

CONCLUSION

As serum AMH level increased, there was a nonlinear increase in relative treatment effect of a freeze-only transfer versus a fresh transfer strategy on live birth, and such an effect reaches its maximum in women with high AMH levels.

Pro: Fresh versus frozen embryo transfer. Is frozen embryo transfer the future?

Embryo cryopreservation has been an integral part of ART for close to 40 years and vitrification has boosted overall ART efficacy and safety. Recently, there has been a vivid scientific discussion on whether elective cryopreservation of all embryos (freeze-all) should be pursued for most patients, with a fresh embryo transfer taking place only in selected cases. In terms of efficacy, the available evidence suggests that the freeze-all strategy leads to higher live birth rates after the first embryo transfer compared to the conventional strategy in high responders, while there is no difference in normal responders. There is no evidence to suggest that the freeze-all strategy is inferior to the conventional strategy of fresh transfer when comparing cumulative live birth rates using data from all available randomized controlled trials. The incidence of ovarian hyperstimulation syndrome is significantly reduced in the freeze-all policy. However, regarding obstetric complications and neonatal outcomes, the evidence suggests that each strategy is associated with certain risks and, therefore, there is no approach that could be unequivocally accepted as safer. Similarly, limited evidence does not support the notion that patients would be universally against freeze-all owing to the inevitable delay in pregnancy achievement. Finally, the cost-effectiveness of freeze-all is likely to vary in different settings and there have been studies supporting that this policy can be, under certain conditions, cost-effective. Adoption of the freeze-all policy can also allow for more flexible treatment strategies that have the potential to increase efficacy, reduce cost and make treatment easier for patients and clinics. Importantly, freeze-all does not require the use of any experimental technologies, further training of personnel or the costly acquisition of new equipment. For these reasons, transitioning to the freeze-all policy for most patients appears to be the next logical step in ART.

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.

Improved clinical outcomes after non-invasive oocyte selection and Day 3 eSET in ICSI patients

BACKGROUND

Non-invasive oocyte quality scoring, based on cumulus gene expression analysis, in combination with morphology scoring, can increase the clinical pregnancy (CPR) and live birth rates (LBR) in Day 3 eSET (elective single embryo transfer) ICSI patients. This was first investigated in a pilot study and is now confirmed in a large patient cohort of 633 patients. It was investigated whether CPR, LBR and time-to-pregnancy could be improved by analyzing the gene expression profile of three predictive genes in the cumulus cells, compared to patients with morphology-based embryo selection only.

METHODS

A large interventional, non-randomized, assessor-blinded cohort study with 633 ICSI patients was conducted in a tertiary fertility center. Non-PCOS patients, 22-39 years old, with good ovarian reserve, were stimulated with HP-hMG using a GnRH antagonist protocol and planned for fresh Day 3 eSET. The cumulus cells from individually denuded oocytes were ranked by a lab-developed cumulus cell test: qRT-PCR for three predictive genes (CAMK1D, EFNB2 and SASH1) and two control genes (UBC, B2M). The embryo selected for transfer was highest ranked from the pool of morphologically transferable Day 3 embryos. Patients in the control (n = 520) and experimental arm (n = 113) were compared for clinical pregnancy and live birth, using a weighted generalized linear model, and time-to-pregnancy using Kaplan-Meier curves.

RESULTS

The CPR was 61% in the experimental arm (n = 113) vs 29% in the control arm (n = 520, p < 0.0001). The LBR in the experimental arm (50%) was significantly higher than in the control arm (27%,p < 0.0001). Time-to-pregnancy was significantly shortened by 3 transfer cycles independent of the number of embryos available on Day 3 (Kaplan-Meier, p < 0.0001). Cumulus cell tested patients < 35 years (n = 65) or ≥ 35 years (n = 48) had a CPR of 62 and 60% respectively (ns). For cumulus cell tested patients with 2, 3-4, or > 4 transferable embryos, the CPR was 66, 52, and 67% (ns) respectively, and thus independent of the number of transferable embryos on Day 3.

CONCLUSIONS

This study provides further evidence of the clinical usefulness of the non-invasive cumulus cell test over time in a larger patient cohort.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03659786 / NCT02962466 (Registered 6Sep2018/11Nov2016, retrospectively registered.

Risk Factors for Different Types of Pregnancy Losses: Analysis of 15,210 Pregnancies After Embryo Transfer

OBJECTIVE

To evaluate the risk factors for different types of pregnancy losses after embryo transfer (ET).

DESIGN

Retrospective cohort study.

SETTING

Reproductive medicine center.

PARTICIPANTS

A total of 15,210 pregnancies after fresh and frozen-thawed embryo transfer between January 2014 and June 2019.

MAIN OUTCOME MEASURES

The primary outcome was pregnancy loss (PL) throughout the entire pregnancy. Secondary outcomes were non-visualized PL, early miscarriage, late miscarriage, and stillbirth.

METHODS

The effect of patients' baseline characteristics and IVF/ICSI cycle-specific factors on the risk of PL after fresh and frozen-thawed ET was determined by multivariate logistic regression analysis.

RESULTS

Compared to women under 35 years old, those between 35 and 40 had an increased risk of early miscarriage [odds ratio (OR) 1.49, 95% confidence interval (CI) 1.22-1.83], while those after 40 appeared to have an increased risk of both early miscarriage (OR 3.82, 95% CI 2.65-5.51) and late miscarriage (OR 2.79, 95% CI 1.64-4.77). Overweight patients were observed to have a higher risk of late miscarriage (OR 1.38, 95% CI 1.16-1.65), while obese patients showed a higher risk of both early miscarriage (OR 1.47, 95% CI 1.14-1.91) and late miscarriage (OR 1.80, 95% CI 1.33-2.44). Polycystic ovary syndrome (PCOS) was an independent risk factor for late miscarriage (OR 1.58, 95% CI 1.28-1.96), and the detrimental effect of PCOS was independent of obesity status. Women with uterine factors had a higher risk of early miscarriage (OR 1.77 (95% CI 1.32-2.38) than women without uterine factors. A negative correlation was observed between the thickness of the endometrium and PL (OR 0.95 95% CI 0.92-0.97). There was an increased risk of PL after frozen-thawed ET versus fresh ET (OR 1.12, 95% CI 1.01-1.24). Women who transferred ≥2 embryos showed lower risk of overall PL than women who transferred a single embryo, with adjusted ORs ranged from 0.57~0.94. However, women who transferred three embryos demonstrated a higher risk of late miscarriage than women who transferred a single embryo (OR 2.23, 95% CI 1.36-3.66).

CONCLUSIONS

Patients with uterine factors demonstrated higher risk of early miscarriage and stillbirth. Being overweight, PCOS, and transferring three embryos was associated with late miscarriage. Being aged 40 and over, obese, and using frozen embryo transfer was associated with early and late miscarriage.

The freeze-all strategy after IVF: which indications?

The freeze-all strategy is gaining popularity worldwide as an alternative to the conventional fresh embryo transfer. It consists of cryopreservation of the entire embryo cohort and the embryo transfer in a subsequent cycle that takes place separately from ovarian stimulation. The freeze-all strategy was initially a 'rescue' strategy for women at high risk of ovarian hyperstimulation syndrome; however, this approach has been extended to other indications as a scheduled strategy to improve implantation rates. This assumes that ovarian stimulation can alter endometrial receptivity in fresh cycles owing to the effect of supraphysiological levels of steroids on endometrial maturation. The procedure, however, has not been associated with increased live birth rates in all infertile couples, and concerns have been raised about the occurrence of several adverse perinatal outcomes. It is, therefore, crucial to identify in which subgroups of patients a freeze-all strategy could be beneficial. The aim of this review is to summarize current scientific research in this field to highlight potential indications for this strategy and to guide clinicians in their daily practice.

Should we still perform fresh embryo transfers in ART?

An increasing number of researchers have alluded to the potential benefit of deferring the transfer of embryos produced during assisted reproductive technologies (ARTs) away from ovarian stimulation, using cryopreservation to enable this. The scientific evidence that may justify this recent trend in the use of the so-called 'freeze-all strategy' includes early, mostly small randomised controlled trials that have demonstrated an increase in live birth rates after elective embryo cryopreservation in certain patient populations, as well as evidence from cohort studies and retrospective analyses. What are the risks and benefits of freeze-all strategies in ART, who are the patients in whom it is likely to be advantageous, and does the current evidence allow us to identify situations when deciding that a fresh embryo transfer would be counter-productive? ART professionals are often faced with challenging clinical decisions regarding the best course of treatment for their patient. The purpose of this opinion paper is to provide a clinical guide for whether to perform a fresh embryo transfer or to opt for freezing all embryos in specific situations.

Development of children born from freeze-only versus fresh embryo transfer: follow-up of a randomized controlled trial

OBJECTIVE

To compare the longer-term development outcomes in children born after freeze-only versus fresh embryo transfer (ET) in women with an ovulatory cycle.

DESIGN

Long-term follow-up study (NCT04099784) of babies born alive after the first ET in a randomized controlled trial (RCT) comparing ongoing pregnancy and live birth rates after use of a freeze-only versus fresh ET strategy (NCT02471573).

SETTING

Private clinic.

PATIENT(S)

Of 391 couples randomized to each treatment group in the RCT, 132 (97 singleton/35 twins) and 123 (95 singleton/28 twins) in the freeze-only and fresh ET groups had live birth; 113 parents (86%) from the freeze-only group (147 babies) and 99 (80%) from the fresh ET group (120 babies) returned questionnaires for this follow-up study.

INTERVENTION(S)

Use of a freeze-only or fresh ET strategy after controlled ovarian hyperstimulation with a follicle-stimulating hormone/gonadotropin-releasing antagonist protocol.

MAIN OUTCOME MEASURE(S)

Developmental status at ≥2 years after birth, determined using the Developmental Red Flags and Ages & Stages Third Edition (ASQ-3) Questionnaires.

RESULT(S)

Mean age of children at the end of follow-up was 37 months. Height (95.0 ± 6.1 vs. 95.7 ± 5.6 cm) and weight (14.9 ± 2.6 vs. 14.8 ± 2.6 kg) were similar in the freeze-only and fresh ET groups (results were similar when singletons and twins were analyzed separately). Overall, ASQ-3 scores for problem solving were significantly better in the freeze-only versus fresh ET group (overall: 53.6 ± 8.4 vs. 51.1 ± 10.2), with no significant between-group difference when singletons (52.3 ± 10.1 vs. 51.0 ± 9.9) and twins (55.0 ± 5.5 vs. 51.4 ± 11.1) were analyzed separately. Fine motor skills scores were numerically higher (with P values approaching statistical significance) in the freeze-only versus fresh ET group in the overall analysis (47.8 ± 11.6 vs. 44.9 ± 12.6) and twins (49.85 ± 8.72 vs. 43.93 ± 12.71), but not singletons (46.0 ± 13.4 vs. 45.4 ± 12.6). The overall proportion of children with abnormal ASQ-3 (6.8% vs. 8.3%) or abnormal Red Flags (5.4% vs. 6.7%) findings in the freeze-only and fresh ET groups was low and did not differ significantly between groups.

CONCLUSION(S)

These data provide physicians with additional information on which to base decisions about the relative merits of different approaches to infertility treatment. There do not appear to be any grounds for concern about worse outcomes after use of a freeze-only strategy. However, additional studies comparing childhood development after a freeze-only strategy, fresh ET, and natural cycles are needed before firm conclusions can be drawn.