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

Immediate versus delayed single blastocyst transfer following the first stimulated IVF cycle in the freeze-all strategy: a study protocol for a randomised controlled trial

INTRODUCTION

In recent years, the use of frozen embryo transfers (FET) has rapidly increased following the freeze-all strategy due to the advantages of increased maternal safety, improved pregnancy rates, lower ectopic pregnancy rates and better obstetric and neonatal outcomes. Currently, there is still no good scientific evidence to support when to perform FET following a stimulated in vitro fertilisation (IVF) cycle in the freeze-all strategy.

METHODS/ANALYSIS

This will be a randomised controlled trial. A total of 828 women undergoing their first FET following their first stimulated IVF cycle in the freeze-all strategy will be enrolled and randomised into one of the following groups according to a computer-generated randomisation list: (1) the immediate group, in which FET will be performed in the first menstrual cycle following the stimulated IVF cycle; or (2) the delayed group, in which FET will be performed at least in the second menstrual cycle following the stimulated IVF cycle. The primary outcome will be live birth, which is defined as the delivery of any infants at ≥22 gestational weeks with heartbeat and breath.

ETHICS/DISSEMINATION

Ethical approval was granted by the Ethics Committee of Assisted Reproductive Medicine at the Shanghai JiAi Genetics & IVF Institute (JIAI E2019-15). Written informed consent will be obtained from each woman before any study procedure is performed, according to good clinical practice. The results of this trial will be disseminated in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04371783.

Competent blastocyst and receptivity endometrium improved clinical pregnancy in fresh embryo transfer cycles: a retrospective cohort study

BACKGROUND

Embryo quality is usually regarded as a key predictor of successful implantation and clinical pregnancy potential. The identification of embryos that have the capacity to implant and result in a healthy pregnancy is a crucial part of in vitro fertilization (IVF). Usually, morphologically high-quality embryos are chosen for embryo transfer in IVF treatment. The aim of this study was to assess the association between the available blastocyst formation rate and the clinical pregnancy outcome following the first fresh embryo transfer cycle and provide systematic individual treatment to adjust endometrial receptivity for the next transfer cycle.

METHODS

This retrospective, single-center study included 512 fresh embryo transfers conducted between 11/2019 and 08/2021, which consisted of 385 cleavage-stage (Day 3) and 127 blastocyst-stage (Day 5) embryo transfers. The two groups were divided into a clinical pregnancy group and a nonclinical pregnancy group for comparison. The association between the available blastocyst formation rate and the clinical pregnancy rate in the Day 3 and Day 5 transfer groups were considered.

RESULTS

In the Day 3 group, there were 275 clinical pregnancies, and the clinical pregnancy rate was 71.43%. Although the two pronuclei (2PN) oocyte rate and available embryo rate at Day 3 were significantly higher in the clinical pregnancy group than the nonclinical pregnancy group (P < 0.05), the blastocyst formation rate and the available blastocyst formation rate were not significantly different between the clinical pregnancy group and the nonclinical pregnancy group (P > 0.05). In the Day 5 group, there were 81 clinical pregnancies, and the clinical pregnancy rate was 63.78%. No baseline characteristics showed any obvious differences between the clinical pregnancy group and nonclinical pregnancy group (P > 0.05). The blastocyst formation rate in the nonclinical pregnancy group was higher than that in the clinical pregnancy group, but the difference was not statistically significant (81.06% vs. 77.03%, P = 0.083). Interestingly, the available blastocyst formation rate and the Day 5 available blastocyst formation rate were significantly higher in the nonclinical pregnancy group than the clinical pregnancy group (66.19% vs. 60.79%, P = 0.014; 54.58% vs. 46.98%, P = 0.007).

CONCLUSIONS

In fresh cycles, the available blastocyst formation rate was not associated with the clinical pregnancy outcome for Day 3 embryo transfers, and the available blastocyst formation rate was not positively correlated with the clinical pregnancy outcome for Day 5 embryo transfers.

Study on the optimal time limit of frozen embryo transfer and the effect of a long-term frozen embryo on pregnancy outcome

In this retrospective study conducted at Sichuan Jinxin Xinan Women and Children's Hospital spanning January 2015 to December 2021, our objective was to investigate the impact of embryo cryopreservation duration on outcomes in frozen embryo transfer. Participants, totaling 47,006 cycles, were classified into 3 groups based on cryopreservation duration: ≤1 year (Group 1), 1 to 6 years (Group 2), and ≥6 years (Group 3). Employing various statistical analyses, including 1-way ANOVA, Kruskal-Wallis test, chi-square test, and a generalized estimating equation model, we rigorously adjusted for confounding factors. Primary outcomes encompassed clinical pregnancy rate and Live Birth Rate (LBR), while secondary outcomes included biochemical pregnancy rate, multiple pregnancy rate, ectopic pregnancy rate, early and late miscarriage rates, preterm birth rate, neonatal birth weight, weeks at birth, and newborn sex. Patient distribution across cryopreservation duration groups was as follows: Group 1 (40,461 cycles), Group 2 (6337 cycles), and Group 3 (208 cycles). Postcontrolling for confounding factors, Group 1 exhibited a decreased likelihood of achieving biochemical pregnancy rate, clinical pregnancy rate, and LBR (OR < 1, aOR < 1, P < .05). Furthermore, an elevated incidence of ectopic pregnancy was observed (OR > 1, aOR > 1), notably significant after 6 years of freezing time [aOR = 4.141, 95% confidence intervals (1.013-16.921), P = .05]. Cryopreservation exceeding 1 year was associated with an increased risk of early miscarriage and preterm birth (OR > 1, aOR > 1). No statistically significant differences were observed in birth weight or sex between groups. However, male infant birth rates were consistently higher than those of female infants across all groups. In conclusion, favorable pregnancy outcomes align with embryo cryopreservation durations within 1 year, while freezing for more than 1 year may diminish clinical pregnancy and LBRs, concurrently elevating the risk of ectopic pregnancy and preterm birth.

Psychosocial wellbeing shortly after allocation to a freeze-all strategy compared with a fresh transfer strategy in women and men: a sub-study of a randomized controlled trial

STUDY QUESTION

Is the psychosocial wellbeing affected in women and men shortly after allocation to a freeze-all strategy with postponement of embryo transfer compared to a fresh transfer strategy?

SUMMARY ANSWER

In general, psychosocial wellbeing (i.e. emotional reactions to the treatment, quality-of-life, infertility-related stress, and marital benefit) was similar in women and men allocated to a freeze-all versus those allocated to a fresh-transfer strategy 6 days after disclosure of treatment strategy (i.e. 4 days after oocyte retrieval), although women in the freeze-all group reported a slightly higher degree of depressive symptoms and mood swings compared to women in the fresh transfer group.

WHAT IS KNOWN ALREADY

The use of a freeze-all strategy, i.e. freezing of the entire embryo cohort followed by elective frozen embryo transfer in subsequent cycles has increased steadily over the past decade in assisted reproductive technology (ART). This strategy essentially eliminates the risk of ovarian hyperstimulation syndrome and has proven beneficial regarding some reproductive outcomes in subgroups of women. However, patients experience a longer time interval between oocyte retrieval and embryo transfer, hence a longer time to pregnancy, possibly adding additional stress to the ART treatment. So far, little focus has been on the possible psychosocial strains caused by postponement of embryo transfer.

STUDY DESIGN, SIZE, DURATION

This is a self-reported questionnaire based sub-study of a multicentre randomized controlled trial (RCT) including 460 women and 396 male partners initiating their first, second, or third treatment cycle of invitro fertilisation or intracytoplasmic sperm injection (ICSI) from May 2016 to September 2018. This sub-study was included in the primary project protocol and project plan for the RCT, as psychosocial wellbeing was considered a secondary outcome.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women from eight public fertility clinics in Denmark and Sweden and one private clinic in Spain were randomized in a 1:1 ratio on the day of inclusion (menstrual cycle day 2 or 3) to either a freeze-all strategy with postponement of embryo transfer to a subsequent modified natural menstrual cycle or a fresh transfer strategy with embryo transfer in the hormone stimulated cycle. Treatment allocation was blinded until the day of the ovulation trigger. Women and their male partners were asked to complete a validated self-reported questionnaire 6 days after unblinding of treatment group allocation, corresponding to 4 days after oocyte retrieval, investigating their psychosocial wellbeing related to the treatment defined as emotional reactions to the treatment, quality-of-life, infertility-related stress, and marital benefit. The questionnaire included items from the Copenhagen Multi-Centre Psychosocial Infertility (COMPI) Fertility Problem Stress Scales and the COMPI Marital Benefit Measure.

MAIN RESULTS AND THE ROLE OF CHANCE

Baseline characteristics were comparable between the two groups for both women and men. In total, response rates were 90.7% for women and 90.2% for men. In the freeze-all group, 207 women and 179 men completed the questionnaire compared with 204 women and 178 men in the fresh transfer group. Men in the two treatment groups did not differ in any of the explored aspects of psychosocial wellbeing (i.e. emotional reactions to the treatment, quality-of-life, infertility-related stress, and marital benefit) 6 days after disclosure of treatment strategy. Women in the freeze-all group reported a slightly higher degree of depressive symptoms (P = 0.045) and mood swings (P = 0.001) (i.e. variables included in 'emotional reactions to treatment') compared to women in the fresh transfer group. When adjusted for multiple testing, depressive symptoms were no longer significantly different between the two groups. No additional differences in psychosocial wellbeing were found. Self-reported quality-of-life during treatment was also rated as similar between the two groups in both women and men, but was slightly lower than they would rate their quality-of-life when not in fertility treatment.

LIMITATIONS, REASONS FOR CAUTION

Although response rates were high, selection bias cannot be excluded. As this study was an RCT, we assume that psychosocial characteristics of the participants were equally distributed in the two groups, thus it is unlikely that the identified psychosocial differences between the freeze-all and fresh transfer group were present already at baseline. Furthermore, the questionnaire was completed as a one-time assessment 4 days after oocyte retrieval, thus not reflecting the whole treatment process, whereas an assessment after the full completed treatment cycle is needed to draw firm conclusions about the psychosocial consequences of the whole waiting period. However, a question posted that late would be highly biased on whether or not a pregnancy had been achieved.

WIDER IMPLICATIONS OF THE FINDINGS

The results indicate that individuals in the freeze-all group exhibited slightly higher levels of depressive symptoms and mood swings compared to those in the fresh transfer group. Nevertheless, it is important to note that any worries related to potential emotional strains stemming from delaying embryo transfer should not overshadow the adoption of a freeze-all approach in cases where it is clinically recommended. As long as patients are provided with comprehensive information about the treatment strategy before initiating the process, it is worth emphasising that other aspects of psychosocial wellbeing were comparable between the two groups.

STUDY FUNDING/COMPETING INTEREST(S)

The study is part of the Reprounion collaborative study, co-financed by the European Union, Interreg V Öresund-Kattegat-Skagerrak. L.P. reports financial support from Merck A/S. H.S.N. reports grants from Freya Biosciences ApS, Ferring Pharmaceuticals, BioInnovation Institute, Ministry of Education, Novo Nordic Foundation, Augustinus Fonden, Oda og Hans Svenningsens Fond, Demant Fonden, Ole Kirks Fond and Independent Research Fund Denmark and personal fees from Ferring Pharmaceuticals, Merck A/S, Astra Zeneca, Cook Medical, IBSA Nordic and Gedeon Richter. H.S.N is founder and chairman of the Maternity Foundation and co-developed the Safe Delivery App (non-profit). N.C.F. reports grants from Gedeon Richter, Merck A/S, Cryos International and financial support from Ferring Pharmaceuticals, Merck A/S and Gedeon Richter. N.C.F. is chairman in the steering committee for the guideline groups for The Danish Fertility Society (non-profit). P.H. reports honoraria from Merch A/S, IBSA Nordic and Gedeon Richter. A.L.M.E. reports grants and financial support from Merck A/S and Gedeon Richter. A.P. reports grants from Gedeon Richter, Ferring Pharmaceuticals, Merck A/S and personal fees from Preglem S.A., Novo Nordic Foundation, Ferring Pharmaceuticals, Gedeon Richter, Cryos International, Merch A/S, Theramex and Organon and the lend of embryoscope to the institution from Gedeon Richter. All other authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov NCT02746562.

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.

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.

Effect of interval between oocyte retrieval and resuscitation embryo transfer on pregnancy outcomes

Objectives

Resuscitation transfer of embryos after elective cryopreservation has been widely applied in in vitro fertilization-embryo transfer (IVF-ET) therapy for human infertility or sterility owing to higher embryo implantation rates. This method separates oocyte retrieval from embryo transfer. The optimal time for frozen embryo transfer (FET) remains unknown. Therefore, this study mainly compares the advantages and disadvantages of delayed FET and immediate FET through retrospective analysis.

Methods

We analyzed real world data of patients who underwent resuscitation transplantation between October 2019 and July 2021 at the Reproductive Center of Chengdu Jinjiang Hospital for Women's and Children's Health. Propensity score matching was applied to control potential confounding factors. A total of 5,549 patients who received at least one FET were analyzed. Patients undergoing transplantation within 60 days of oocyte retrieval were included in the immediate FET group (n = 1,265) and those undergoing transplantation > 60 days after retrieval were included in the delayed FET group (n = 4,284).

Results

Live birth rates between the two groups were comparable (45.25% vs. 45.76%, p = 0.757). Moreover, no difference was observed in the rates of biochemical pregnancy (64.50% vs. 66.80%), clinical pregnancy (55.24% vs. 56.83%), ectopic pregnancy (1.47% vs. 1.39%), early miscarriage (14.41% vs. 16.20%), late miscarriage (2.21% vs. 2.09%), singleton premature delivery (16.67% vs. 18.29%), and neonatal deformity (1.97% vs. 1.80%). After stratifying the patients based on the type of embryo transferred, number of embryos transferred, FET protocol, and good prognosis criteria, live birth rates remained comparable between the two groups (p > 0.05).

Conclusion

Pregnancy outcomes were comparable between the immediate and delayed FET groups.

Association between Pet Ownership and Threatened Abortion in Pregnant Women: The China Birth Cohort Study

Background: The aim of this study was to assess the association between pet ownership and threatened abortion (TA) in pregnant Chinese women. Materials and Methods: We enrolled pregnant women from 18 provinces and autonomous regions across China between November 2017 and December 2020. Participants were grouped based on the presence or absence of pet ownership. Pet owners were further sub-grouped based on the presence or absence of close contact with their pets. Pet species included cats, dogs, and both. Generalised linear mixed models, with province as a random effect, were used to estimate the associations between pet ownership and TA. Results: Pet ownership, whether or not one had close contact with pets, was associated with greater odds of TA (OR: 1.30, 95% CI: 1.21, 1.40). Keeping pet cats (OR: 1.24, 95% CI: 1.11, 1.40), dogs (OR: 1.29, 95% CI: 1.18, 1.41), or both cats and dogs (OR: 1.36, 95% CI: 1.04, 1.68) during pregnancy were all risk factors for TA. We observed significant group differences (p for difference < 0.05) in pre-pregnancy body mass index, education levels, and annual household income. Conclusions: Cat or dog ownership during pregnancy was associated with an increased risk of TA, especially among overweight, less educated, or lower-income participants.

The association between embryo storage time and treatment success in women undergoing freeze-all embryo transfer

OBJECTIVE

To investigate the relationship between the embryo frozen time and live birth rate (LBR) in women having a freeze-all cycle.

DESIGN

Retrospective cohort study.

SETTING

Academic hospital.

PATIENT(S)

Women who underwent their first vitrified-warmed cycles from January 2013 to December 2019.

INTERVENTION(S)

Embryo storage time.

MAIN OUTCOME MEASURE(S)

The primary outcome was the LBR.

RESULT(S)

A total of 14,928 women were eligible for the analysis. Women with the frozen time of transferred embryos for 2-5 months were associated with a higher LBR compared with other groups. The results were confirmed by an inverted U curve in the restricted cubic splines before as well as after adjustment for covariables, which suggested that an embryo storage time of 3-4 months was associated with the highest LBR. Subgroup analyses demonstrated that the inverted U curve relationship between embryo storage time and LBR was only observed in women with the high response. Sensitivity analyses in women with at least one good-quality embryo for transfer, in women aged <36 years at embryo transfer, or in women with double cleavage embryo transfer showed that the association remained valid. The association was weakened in women with single blastocyst transfer probably because of the small sample size in these women.

CONCLUSION(S)

An inverted U-shaped relationship was found between embryo storage time and treatment success in women with high ovarian response in freeze-all embryo transfer cycles. Prolonged storage time of >6 months was associated with reduced pregnancy rates.

Immediate versus postponed single blastocyst transfer in modified natural cycle frozen embryo transfer (mNC-FET): a study protocol for a multicentre randomised controlled trial

INTRODUCTION

Today, it is widespread practice to postpone frozen embryo transfer (FET) in a modified natural cycle (mNC) for at least one menstrual cycle after oocyte retrieval and failed fresh embryo transfer or freeze-all. The rationale behind this practice is the concern that suboptimal ovarian, endometrial or endocrinological conditions following ovarian stimulation may have a negative impact on endometrial receptivity and implantation. However, two recent systematic reviews and meta-analyses based on retrospective data did not support this practice. As unnecessary delay in time to transfer and pregnancy should be avoided, the aim of this study is to investigate if immediate single blastocyst transfer in mNC-FET is non-inferior to standard postponed single blastocyst transfer in mNC-FET in terms of live birth rate.

METHODS AND ANALYSIS

Multicentre randomised controlled non-blinded trial including 464 normo-ovulatory women aged 18-40 years undergoing single blastocyst mNC-FET after a failed fresh or freeze-all cycle. Participants are randomised 1:1 to either FET in the first menstrual cycle following the stimulated cycle (immediate FET) or FET in the second or subsequent cycle following the stimulated cycle (postponed FET). The study is designed as a non-inferiority trial and primary analyses will be performed as intention to treat and per protocol.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Scientific Ethical Committee of the Capital Region of Denmark (J-nr.: H-19086300). Data will be handled according to Danish law on personal data protection in accordance with the general data protection regulation. Participants will complete written consent forms regarding participation in the study and storage of blood samples in a biobank for future research. The study will be monitored by a Good Clinical Practice (GCP)-trained study nurse not otherwise involved in the study. The results of this study will be disseminated by publication in international peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT04748874; Pre-results.

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.