Comparison of Pregnancy and Neonatal Outcomes of Single Frozen Blastocyst Transfer Between Letrozole-Induction and HRT Cycles in Patients With Abnormal Ovulation

Abstract

BackgroundThe use of frozen embryo transfer (FET) cycles has dramatically risen. The optimal endometrial preparation method for women undergoing FET is of utmost importance to provide the optimal chances of pregnancy. For patients with abnormal ovulation in particular, there have been few studies on FET protocols; notably, most of these studies focus only on the clinical pregnancy rate or live birth rate (LBR) and pay little attention to the regimen’s safety for offspring.MethodsIt was a retrospective cohort study. First FET cycle with a single blastocyst from whole embryo frozen IVF/ICSI at the Reproductive Center of Third Affiliated Hospital of Zhengzhou University between January 2016 and January 2020. The LBR was the primary outcome of interest. The secondary outcome measures were miscarriage rate and offspring safety, including preterm birth, low birthweight (LBW), small-for-gestational age (SGA), macrosomia and large-for-gestational age (LGA).ResultsIn total, 2782 FET cycles met the eligibility criteria for analysis. Additionally, there were 1178 singleton births from FET cycles. The clinical pregnancy rate was 58.4% in the L-FET group and 54.5% in the HRT group, with no statistical significance (P=.116). The miscarriage rate was higher in the HRT group than in the L-FET group (21.7% vs. 14.3%, P=.005). The LBR was significantly higher in the L-FET group than in the HRT group (49.6% vs. 41.7%, P=.001). Neonatal outcomes were similar between the two groups. After adjustments for confounding factors, the LBR was higher in the L-FET group (aOR 1.30, 95% CI 1.06-1.58). The rate of miscarriage was lower in the L-FET group (aOR 0.63, 95% CI 0.44-0.90).ConclusionFor patients with abnormal ovulation, the L-FET regimen has a higher LBR and lower miscarriage rate than HRT. The neonatal outcomes were similar between the two groups.

Comparison of Perinatal Outcomes of Letrozole-Induced Ovulation and Hormone Replacement Therapy Protocols in Patients With Abnormal Ovulation Undergoing Frozen-Thawed Embryo Transfer: A Propensity Score Matching Analysis

“…Despite no difference in pregnancy outcomes between the two groups, endometrial thickness on the day of embryo transfer in the L-OI group was greater than that in the HRT group in our study, which was consistent with a previous study from our center ( 29 ). The reason may be that the proportion of patients with thin endometrium was relatively high in the HRT group.…”

“…A large retrospective cohort study in Japan in 2017 that included 110,772 FET cycles, which were divided into an LE-induced ovulation group, NC group and HRT group according to the endometrial preparation protocol used, found that neonatal outcomes of the different treatment schemes were basically similar, consistent with our results. A previous study in our center also reached similar conclusions ( 29 ).…”

“…Although the live birth rate was increased in our study by using the L-OI protocol, there was no significant differences between the groups possibly due to a large difference in the number of cases included in the L-OI (502) and HRT (2280) groups. There was also heterogeneity in basic characteristics; a previous study adopted regression analysis for correction ( 29 ), which was different from the 1:1 PSM in our study.…”

The future of frozen-thawed embryo transfer in hormone replacement therapy cycles

“…None of the studies reported a poorer live birth rate (LBR) in letrozole FET compared to HRT FET. Three papers including the only RCT reported similar live birth rate (LBR) [6,7] or ongoing pregnancy rate (OPR) [8], whereas seven retrospective studies reported improved LBR in letrozole FET compared to HRT FET [9–15].…”

Letrozole Supplementation and the Increased Risk of Elevated Progesterone Levels on Trigger Day

“…First, LE is used to prepare the endometrium in the frozen embryo transfer (FET) cycle, and no negative effect on endometrial receptivity has yet been reported (5)(6)(7)(8). Some studies revealed that clinical pregnancy rates and live birth rates in the LE group are significantly higher, and the rate of miscarriage is significantly lower compared to those in the natural and hormone replacement cycle groups (9,10). Second, LE significantly lowers the level of oestradiol and prevents ovarian hyperstimulation syndrome (11), exerting protective effects in patients with breast cancer (12).…”