The interval between oocyte retrieval and frozen-thawed blastocyst transfer does not affect the live birth rate and obstetrical outcomes

The HERA (Hyper-response Risk Assessment) Delphi consensus for the management of hyper-responders in in vitro fertilization

PURPOSE

To provide agreed-upon guidelines on the management of a hyper-responsive patient undergoing ovarian stimulation (OS) METHODS: A literature search was performed regarding the management of hyper-response to OS for assisted reproductive technology. A scientific committee consisting of 4 experts discussed, amended, and selected the final statements. A priori, it was decided that consensus would be reached when ≥66% of the participants agreed, and ≤3 rounds would be used to obtain this consensus. A total of 28/31 experts responded (selected for global coverage), anonymous to each other.

RESULTS

A total of 26/28 statements reached consensus. The most relevant are summarized here. The target number of oocytes to be collected in a stimulation cycle for IVF in an anticipated hyper-responder is 15-19 (89.3% consensus). For a potential hyper-responder, it is preferable to achieve a hyper-response and freeze all than aim for a fresh transfer (71.4% consensus). GnRH agonists should be avoided for pituitary suppression in anticipated hyper-responders performing IVF (96.4% consensus). The preferred starting dose in the first IVF stimulation cycle of an anticipated hyper-responder of average weight is 150 IU/day (82.1% consensus). ICoasting in order to decrease the risk of OHSS should not be used (89.7% consensus). Metformin should be added before/during ovarian stimulation to anticipated hyper-responders only if the patient has PCOS and is insulin resistant (82.1% consensus). In the case of a hyper-response, a dopaminergic agent should be used only if hCG will be used as a trigger (including dual/double trigger) with or without a fresh transfer (67.9% consensus). After using a GnRH agonist trigger due to a perceived risk of OHSS, luteal phase rescue with hCG and an attempt of a fresh transfer is discouraged regardless of the number of oocytes collected (72.4% consensus). The choice of the FET protocol is not influenced by the fact that the patient is a hyper-responder (82.8% consensus). In the cases of freeze all due to OHSS risk, a FET cycle can be performed in the immediate first menstrual cycle (92.9% consensus).

CONCLUSION

These guidelines for the management of hyper-response can be useful for tailoring patient care and for harmonizing future research.

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.

Do live birth rate and obstetric outcomes vary between immediate and delayed embryo transfers following freeze-all cycles?

RESEARCH QUESTION

Do live birth rates (LBR), obstetric and perinatal outcomes vary between women who underwent frozen embryo transfer (ET) in the immediately subsequent menstrual cycle, and with those who underwent delayed frozen ET.

DESIGN

Retrospective cohort study (n = 198) consisting of 119 women who underwent immediate transfer within 30 days of oocyte retrieval (OR) and 79 women who underwent delayed transfer which was performed after >30 days following OR. Either flexible antagonist or flexible progestin-primed ovarian stimulation protocols were started after a baseline ultrasonography on the second or third day of menstrual cycle. Only freeze all cycles were included in the study and all transfers were with hormonal endometrial preparation. Main outcome measures were LBR, birth weight, gestational day at birth and pregnancy complications.

RESULTS

Peak estradiol level on trigger day (2746 vs 2081 pg/ml) and number of metaphase-two oocytes (13 vs 10) were significantly higher in the immediate transfer group. Clinical pregnancy rate per ET was similar between the groups (50.4% vs 44.3%). However, miscarriage rate per positive pregnancy was significantly higher (12.3% vs 31.1%) while LBR per ET was significantly lower (42.9% vs 26.6%) in the delayed transfer group. Median gestational age at delivery were 267.5 and 268 days in the immediate and delayed transfer groups. Median birthweight was significantly higher in the delayed transfer group (3520 vs 3195 g). Adjusted analyses also suggest similar LBR with immediate and delayed transfer.

CONCLUSION(S)

Frozen ET in the immediate menstrual cycle and delayed ET, after a freeze all strategy did not show significant difference in terms of LBR after adjustment. Obstetric and perinatal outcomes of frozen ET in the immediate menstrual cycle appear reassuring.

Immediate versus delayed frozen embryo transfer in patients following a stimulated IVF cycle: a randomised controlled trial

STUDY QUESTION

Is there any difference in the ongoing pregnancy rate after immediate versus delayed frozen embryo transfer (FET) following a stimulated IVF cycle?

SUMMARY ANSWER

Immediate FET following a stimulated IVF cycle produced significantly higher ongoing pregnancy and live birth rate than did delayed FET.

WHAT IS KNOWN ALREADY

Embryo cryopreservation is an increasingly important part of IVF, but there is still no good evidence to advise when to perform FET following a stimulated IVF cycle. All published studies are retrospective, and the findings are contradictory.

STUDY DESIGN, SIZE, DURATION

This was a randomised controlled non-inferiority trial of 724 infertile women carried out in two fertility centres in China between 9 August 2017 and 5 December 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Infertile women having their first FET cycle after a stimulated IVF cycle were randomly assigned to either (1) the immediate group in which FET was performed in the first menstrual cycle following the stimulated IVF cycle (n = 362) or (2) the delayed group in which FET was performed in the second or later menstrual cycle following the stimulated IVF cycle (n = 362). All FET cycles were performed in hormone replacement cycles. The randomisation sequence was generated using an online randomisation program with block sizes of four. The primary outcome was the ongoing pregnancy rate, defined as a viable pregnancy beyond 12 weeks of gestation. The non-inferiority margin was -10%. Analysis was performed by both per-protocol and intention-to-treat approaches.

MAIN RESULTS AND THE ROLE OF CHANCE

Women in the immediate group were slightly younger than those in the delayed group (30.0 (27.7-33.5) versus 31.0 (28.5-34.2), respectively, P = 0.006), but the proportion of women ≤35 years was comparable between the two groups (308/362, 85.1% in the immediate group versus 303/362, 83.7% in the delayed group). The ongoing pregnancy rate was 49.6% (171/345) in the immediate group and 41.5% (142/342) in the delayed group (odds ratios 0.72, 95% CI 0.53-0.98, P = 0.034). The live birth rate was 47.2% (163/345) in the immediate group and 37.7% (129/342) in the delayed group (odds ratios 0.68, 95% CI 0.50-0.92, P = 0.012). The miscarriage rate was 13.2% (26 of 197 women) in the immediate group and 24.2% (43 of 178 women) in the delayed group (odds ratios 2.10; 95% CI 1.23-3.58, P = 0.006). The multivariable logistic regression, which adjusted for potential confounding factors including maternal age, number of oocytes retrieved, embryo stage at transfer, number of transferred embryos/blastocysts, reasons for FET, ovarian stimulation protocol and trigger type, demonstrated that the ongoing pregnancy rate was still higher in the immediate group.

LIMITATIONS, REASON FOR CAUTION

Despite randomisation, the two groups still differed slightly in the age of the women at IVF. The study was powered to consider the ongoing pregnancy rate, but the live birth rate may be of greater clinical interest. Conclusions relating to the observed differences between the treatment groups in terms of live birth rate should, therefore, be made with caution.

WIDER IMPLICATIONS OF THE FINDINGS

Immediate FET following a stimulated IVF cycle had a significantly higher ongoing pregnancy and live birth rate than delayed FET. The findings of this study support immediate FET after a stimulated IVF cycle.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used and no competing interests were declared.

TRIAL REGISTRATION NUMBER

ClinicalTials.gov identifier: NCT03201783.

TRIAL REGISTRATION DATE

28 June 2017.

DATE OF FIRST PATIENT’S ENROLMENT

9 August 2017.

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

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

Immediate versus postponed frozen embryo transfer after IVF/ICSI: a systematic review and meta-analysis

BACKGROUND

In Europe, the number of frozen embryo transfer (FET) cycles is steadily increasing, now accounting for more than 190 000 cycles per year. It is standard clinical practice to postpone FET for at least one menstrual cycle following a failed fresh transfer or after a freeze-all cycle. The purpose of this practice is to minimise the possible residual negative effect of ovarian stimulation on the resumption of a normal ovulatory cycle and receptivity of the endometrium. Although elective deferral of FET may unnecessarily delay time to pregnancy, immediate FET may be inefficient in a clinical setting, following an increased risk of irregular ovulatory cycles and the presence of functional cysts, increasing the risk of cycle cancellation.

OBJECTIVE AND RATIONALE

This review explores the impact of timing of FET in the first cycle (immediate FET) versus the second or subsequent cycle (postponed FET) following a failed fresh transfer or a freeze-all cycle on live birth rate (LBR). Secondary endpoints were implantation, pregnancy and clinical pregnancy rates (CPR) as well as miscarriage rate (MR).

SEARCH METHODS

We searched PubMed (MEDLINE) and EMBASE databases for MeSH and Emtree terms, as well as text words related to timing of FET, up to March 2020, in English language. There were no limitations regarding year of publication or duration of follow-up. Inclusion criteria were subfertile women aged 18-46 years with any indication for treatment with IVF/ICSI. Studies on oocyte donation were excluded. All original studies were included, except for case reports, study protocols and abstracts only. Covidence, a Cochrane-tool, was used for sorting and screening of literature. Risk of bias was assessed using the Robins-I tool and the quality of evidence using the Grading of Recommendations, Assessment, Development and Evaluation framework.

OUTCOMES

Out of 4124 search results, 15 studies were included in the review. Studies reporting adjusted odds ratios (aOR) for LBR, CPR and MR were included in meta-analyses. All studies (n = 15) were retrospective cohort studies involving a total of 6,304 immediate FET cycles and 13,851 postponed FET cycles including 8,019 matched controls. Twelve studies of very low to moderate quality reported no difference in LBR with immediate versus postponed FET. Two studies of moderate quality reported a statistically significant increase in LBR with immediate FET and one small study of very low quality reported better LBR with postponed FET. Trends in rates of secondary outcomes followed trends in LBR regarding timing of FET. The meta-analyses showed a significant advantage of immediate FET (n =2,076) compared to postponed FET (n =3,833), with a pooled aOR of 1.20 (95% CI 1.01-1.44) for LBR and a pooled aOR of 1.22 (95% CI 1.07-1.39) for CPR.

WIDER IMPLICATIONS

The results of this review indicate a slightly higher LBR and CPR in immediate versus postponed FET. Thus, the standard clinical practice of postponing FET for at least one menstrual cycle following a failed fresh transfer or a freeze-all cycle may not be best clinical practice. However, as only retrospective cohort studies were assessed, the presence of selection bias is apparent, and the quality of evidence thus seems low. Randomised controlled trials including data on cancellation rates and reasons for cancellation are highly needed to provide high-grade evidence regarding clinical practice and patient counselling.

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.

Risk of small for gestational age is reduced after frozen compared with fresh embryo transfer in endometriosis

RESEARCH QUESTION

What are the perinatal outcomes and especially the risk of small for gestational age (SGA) babies born after frozen versus fresh embryo transfer in mothers affected by endometriosis undergoing treatment with assisted reproductive technology (ART)?

DESIGN

A cohort study conducted between November 2012 and October 2017, in which infertile women with endometriosis undergoing ART and achieving singleton pregnancies that lasted beyond 12 weeks of gestation were included. Pregnancies obtained after a frozen embryo transfer (FET) were compared with those obtained after a fresh embryo transfer. A total of 339 pregnant women were included: 112 patients in the fresh embryo transfer group and 227 in the FET group. The main outcome was the rate of SGA. Secondary analyses were performed for adverse pregnancy outcomes and perinatal complications.

RESULTS

Of the included women, 109/112 (97.3%) and 222/227 (97.8%) delivered a live child after at least 24 weeks of gestation in the fresh and in the frozen embryo transfer groups, respectively (P = 0.53). The risk of SGA decreased after a FET compared with a fresh embryo transfer (odds ratio [OR] 0.49 [0.25-0.98], P = 0.04) after multivariable analysis. The mean birthweight and the gestational age at delivery were not significantly different between the two study groups. Other pregnancy and perinatal complications were not statistically different between the two study populations.

CONCLUSIONS

The present study of endometriosis-affected women found a significantly lower risk of SGA in patients undergoing frozen, mainly blastocyst, embryo transfer compared with patients undergoing fresh, mainly cleavage stage, embryo transfer.

Delayed versus immediate frozen embryo transfer after oocyte retrieval: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to compare pregnancy outcomes between immediate frozen embryo transfer (FET) performed within the first menstrual cycle after oocyte retrieval and delayed FET following subsequent cycles.

METHODS

PubMed, EMBASE, and Web of Science were searched for eligible studies through January 2020. The main outcome measures were clinical pregnancy rate (CPR), live birth rate (LBR), and pregnancy loss rate (PLR). The effect size was estimated as risk ratio (RR) with 95% confidence interval (CI) using a random effects model. Inter-study heterogeneity was assessed by the I² statistic.

RESULTS

Twelve retrospective cohort studies involving 18,230 cycles were included. The pooled results revealed no significant differences between delayed and immediate FET in CPR (RR 0.94, 95% CI 0.87-1.03; I² = 67.9%), LBR (RR 0.94, 95% CI 0.85-1.03; I² = 67.5%), and PLR (RR 1.05, 95% CI 0.87-1.26; I² = 42.7%). Subgroup analyses of freeze-all cycles showed a marginal decrease of CPR in delayed FET (RR 0.93, 95% CI 0.86-1.00; I² = 53.6%), but no significant changes were observed regarding LBR (RR 0.93, 95% CI 0.85-1.02; I² = 65.2%) and PLR (RR 1.09, 95% CI 0.84-1.41; I² = 59.1%). No statistical differences were found in effect estimates among other subgroup analyses by ovarian stimulation protocol, trigger agent, endometrial preparation regimen, and embryo stage.

CONCLUSION

Timing of the first FET after oocyte retrieval was not significantly associated with pregnancy outcomes. This finding refutes the current common practice to delay FET after oocyte retrieval and reassures patients who wish to proceed with FET at their earliest convenience. Due to the high heterogeneity and observational nature of included studies, further randomized controlled trials are needed to confirm the results.

The Future of Cryopreservation in Assisted Reproductive Technologies

Societal changes and the increasing desire and opportunity to preserve fertility have increased the demand for effective assisted reproductive technologies (ART) and have increased the range of scenarios in which ART is now used. In recent years, the "freeze-all" strategy of cryopreserving all oocytes or good quality embryos produced in an IVF cycle to transfer later-at a time that is more appropriate for reasons of medical need, efficacy, or desirability-has emerged as an accepted and valuable alternative to fresh embryo transfer. Indeed, improvements in cryopreservation techniques (vitrification) and the development of more efficient ovarian stimulation protocols have facilitated a dramatic increase in the practice of elective frozen embryo transfer (eFET). Alongside these advances, debate continues about whether eFET should be a standard treatment option available to the whole IVF population or if it is important to identify patient subgroups who are most likely to benefit from such an approach. Achieving successful outcomes in ART, whether by fresh or frozen embryo transfer, is influenced by a wide range of factors. As well as the efficiency of IVF and embryo transfer protocols and techniques, factors affecting implantation include maternal aging, sperm quality, the vaginal and endometrial microbiome, and peri-implantation levels of serum progesterone. The safety of eFET, both during ART cycles and on longer-term obstetric and neonatal outcomes, is also an important consideration. In this review, we explore the benefits and risks of freeze-all strategies in different scenarios. We review available evidence on the outcomes achieved with elective cryopreservation strategies and practices and how these compare with more traditional IVF cycles with fresh embryo transfers, both in the general IVF population and in subgroups of special interest. In addition, we consider how to optimize and individualize "freeze-all" procedures to achieve successful reproductive outcomes.

Timing of frozen-thawed embryo transfer after controlled ovarian stimulation in a non-elective freeze-all policy

Background

Non-elective freeze-all policy has been increasingly utilized in assisted reproductive treatment, but the optimal timing of frozen-thawed embryo transfer (FET) after controlled ovarian stimulation (COS) remains to be investigated.

Methods

This retrospective cohort study included 2,998 patients who underwent their first FETs after the first COS cycles using the non-elective freeze-all strategy from Jan 2013 to Dec 2016 at a tertiary-care academic medical center. Patients were divided into the "immediate" group in which FET took place within the first menstrual cycle after oocyte retrieval, and the "delayed" group where FET started after one or more menstrual cycles following COS.

Results

The mean interval between oocyte retrieval and FET was 33.3±5.8 days in the immediate group (n=280; 9.3%) and 91.3±19.4 days in the delayed group (n=2,718; 90.7%). Cycles with delayed FET had a significantly lower live birth rate than those with immediate FET before [1,246/2,718 (45.8%) vs. 156/280 (55.7%); P=0.002] and after propensity score matching (PSM) [123/280 (43.9%) vs. 156/280 (55.7%); P=0.005]. When controlling for a number of confounding factors by multivariable logistic regression analysis, the risk remained significant with the adjusted odds ratio (aOR) [95% confidence interval (CI)] of 0.69 (0.53-0.90) and 0.60 (0.42-0.85) before and after matching, respectively.

Conclusions

Performing FET immediately within the first menstrual cycle following COS was associated with a higher chance to achieve live birth compared with delaying FET to subsequent cycles in a non-elective freeze-all policy. However, further randomized controlled trials are still needed to confirm this conclusion.

Frozen embryo transfer at the cleavage stage can be performed within the first menstrual cycle following the freeze-all strategy without adversely affecting the live birth rate: A STROBE-compliant retrospective study

Thus far, all clinical trials evaluating the efficacy of embryo transfer strategies have selectively delayed the first frozen embryo transfer (FET) by at least 1 menstrual cycle. Nevertheless, this approach, which is based solely on clinical experience, may create unnecessary psychological stress on infertile patients who are anxious to conceive as soon as possible. This study aimed to investigate whether the time interval between oocyte retrieval and subsequent FET affects reproductive outcomes.We implemented a large retrospective cohort study in a single assisted reproductive technology (ART) unit at a university-based hospital, including 1540 autologous FET cycles performed in freeze-all cycles. The beginning of the FET was classified as either 'cycle 1' (performing FET within the first menstrual cycle) or 'cycle ≥2' (performing FET after one or more menstrual cycles). Live birth rate (LBR) was the primary outcome of our study.The mean interval for 'cycle 1' and 'cycle ≥2' FETs was 25.72 ± 5.10 days and 75.33 ± 24.85 days, respectively (P < .001). The type of controlled ovarian hyperstimulation (COH) and endometrial preparation protocols differed significantly between groups (P = .008 and P = .004, respectively). However, FET groups were similar in many ways. Univariate analysis showed that there was no significant difference in LBR between the different cycles (33.1% after 'cycle 1' FET vs 34.2% after 'cycle ≥2' FET, P = .68). To evaluate whether LBR remained unchanged after adjustment for potential confounders, we performed multivariate logistic regression. FET timing had no significant impact on LBR in the first FET (odds ratio [OR]: 1.06, 95% confidence interval [CI]: 0.80-1.39).In accordance with the present study, it might not be necessary for clinicians to wait more than 1 menstrual cycle before performing FET. This allows us to reduce otiose deferment in FET, without adversely affecting reproductive outcomes.