Is a frozen embryo transfer in a programmed cycle really the best option?

Perinatal outcomes of progesterone in natural frozen-thawed embryo transfer pregnancies: insights from 2 randomized controlled trials

OBJECTIVE

To explore whether progesterone supplementation during luteal phase and early pregnancy after a natural frozen-thawed embryo transfer (NC-FET) cycle affects perinatal outcomes.

DESIGN

A secondary data analysis study on the basis of 2 randomized control trials taking place during 2008-2011 and 2013-2018 at 2 university hospitals in Sweden.

SUBJECTS

A total of 923 women undergoing an NC-FET cycle. The present study included all women who became pregnant after treatment and delivered a single live-born infant (N = 227).

INTERVENTIONS

Study participants were randomized to receive luteal phase vaginal progesterone supplementation until gestational week 8 (n = 136) or to the standard of care that was no progesterone supplementation (n = 91).

MAIN OUTCOME MEASURES

We assessed the incidence of obstetric and neonatal outcomes. Furthermore, we calculated the odds ratios with 95% confidence intervals representing the likelihood of developing gestational hypertensive disorders. Odds ratios were adjusted for participants' demographics (model 1) or both demographic and in vitro fertilization treatment variables (model 2).

RESULTS

Apart from a slightly higher maternal age in the group receiving progesterone supplementation, the subjects in both groups were otherwise comparable in terms of infertility diagnosis, fertilization mode, embryo stage, and number of embryos transferred. Our results revealed a higher proportion of infants delivered with birth weights in the normal range after progesterone supplementation (82.4% vs. 70.3% respectively). Furthermore, pregnancies after progesterone supplementation in NC-FET cycles showed a numerically lower incidence of gestational hypertensive disorders; however, this difference did not reach statistical significance (4.4% vs. 11.1%). A similar pattern was noted in the logistic regression analyses performed. No differences were observed regarding other major adverse obstetric or neonatal outcomes.

CONCLUSION

Our study demonstrates the absence of harmful perinatal effects associated with the use of vaginal progesterone supplementation at the luteal phase and early pregnancy of an NC-FET cycle. These findings have increased generalizability across other populations and are particularly significant given the growing utilization of cryopreservation and freeze-all practice in assisted reproduction. The associations noted between progesterone supplementation and certain perinatal outcomes warrant further investigation.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Frozen embryo transfer and preeclampsia: where is the link?

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

The impact of timing modified natural cycle frozen embryo transfer based on spontaneous luteinizing hormone surge

PURPOSE

To evaluate whether adjusting timing of modified natural cycle frozen embryo transfer (mNC-FET) 1 day earlier in the setting of a spontaneous LH surge has an impact on pregnancy outcomes.

METHODS

This retrospective cohort study evaluated all mNC-FET with euploid blastocysts from May 1, 2016 to March 30, 2019, at a single academic institution. Standard protocol for mNC-FET included ultrasound monitoring and hCG trigger when the dominant follicle and endometrial lining were appropriately developed. Patients had serum LH, estradiol, and progesterone checked on day of trigger. If LH was ≥ 20 mIU/mL, trigger was given that day and FET was performed 6 days after surge (LH/HCG+6), with the intent of transferring 5 days after ovulation. If LH was < 20 mIU/mL, FET was performed 7 days after trigger (hCG+7). Primary outcomes included clinical pregnancy and live birth rates. To account for correlation between cycles, a generalized estimating equation (GEE) method for multivariable logistic regression was used.

RESULTS

Four hundred fifty-three mNC-FET cycles met inclusion criteria, of which 205 were in the LH/HCG+6 group and 248 were in the HCG+7 group. The overall clinical pregnancy rate was 64% and clinical miscarriage rate was 4.8%, with similar rates between the two groups. The overall live birth rate was 60.9% (61.0% in LH/HCG+6 group and 60.9% in HCG+7 group). After implementing GEE, the odds of CP (aOR 0.97, 95% CI [0.65-1.45], p = 0.88) and LB (aOR 0.98, 95% CI [0.67-1.45], p = 0.93) were similar in both groups.

CONCLUSIONS

In our study cohort, mNC-FET based on LH/HCG+6 versus HCG+7 had similar pregnancy outcomes.