P-612 Comparison the effectiveness and safety of letrozole-stimulated and hormone replacement treatment in endometrial preparation for frozen embryo transfer in patients with polycystic ovary syndrome
Authors: Wang X , Li Y , Cai S , Li X , Tang Y , Luo K , Zhang S , Lin G , Gong F 
Published: June 2023

Study question

Whether letrozole-stimulated protocol has advantages over hormone replacement therapy (HRT) in frozen embryo transfer in patients with polycystic ovary syndrome (PCOS)?

Summary answer

Letrozole-stimulated protocol is more suitable for endometrial preparation than HRT in patients with PCOS, which can increase the live birth rate and reduce pregnancy complications.

What is known already

The current routine endometrial preparation protocol for women with PCOS is HRT. However, HRT is expensive, and recent studies have found HRT may increase the risk of adverse maternal and neonatal complications such as hypertensive disorders of pregnancy. Letrozole induces mono-ovulatory and has no antiestrogenic effect, and has been found to increase live birth rate compared with clomiphene in fresh embryo cycles. However, Letrozole is rarely used in frozen embryo cycles. Whether letrozole-stimulated protocol is suitable for frozen embryo transfer in patients with PCOS and for whom is suitable is still lack of evidence.

Study design, size, duration

This is a retrospective cohort study involving all frozen embryo transfer cycles with letrozole-stimulated and HRT for PCOS during the period from August 2018 to December 2020 at a tertiary care center.

Participants/materials, setting, methods

A total of 2011 letrozole-stimulated cycles and 2211 HRT cycles were included in the analysis. Multivariate Logistic regression was used to analyze the differences in clinical pregnancy rate, live birth rate, miscarriage rate, the incidence of other pregnancy and obstetric outcomes between letrozole-stimulated protocol and HRT after adjusting for possible confounding factors. Subgroup analysis was used to explore the population for which letrozole-stimulated protocol was suitable.

Main results and the role of chance

After adjusting for confounding, letrozole-stimulated protocol increased the clinical pregnancy rate (OR,1.44; 95%CI,1.21-1.70), live birth rate (OR,1.49; 95%CI,1.27-1.74) and reduced the incidence of miscarriage (OR, 0.71; 95%CI,0.55-0.92), hypertensive disorders of pregnancy (OR, 0.66; 95%CI,0.45,0.98), gestational diabetes mellitus (OR,0.75; 95%CI,0.57,0.98) and cesarean section (OR,0.78; 95%CI,0.61,0.99) than HRT. There were no significant differences in other outcomes such as preterm birth, small for gestational age, and large for gestational age between the two endometrial preparation protocols. Subgroup analysis according to maternal age, BMI, insulin resistance and PCOS classification showed that the live birth rate of letrozole-stimulated protocol was significantly higher than that of HRT in all subgroups.

Limitations, reasons for caution

This study is a retrospective study, the population characteristics of the two endometrial preparation protocols existed differences. Although multivariate logistic regression was used to adjust some factors, the interference of known and unknown factors on the outcomes cannot be completely avoided.

Wider implications of the findings

This retrospective study found letrozole-stimulated protocol has more advantages than HRT, which can improve the live birth rate and reduce the incidence of hypertensive disorders of pregnancy, gestational diabetes mellitus in patients with PCOS. High-quality well-powered randomised clinical trials and possible mechanistic studies are needed to further validate this conclusion.

Trial registration number

NA