Letrozole During Frozen Embryo Transfer in Women With Polycystic Ovarian Syndrome

OBJECTIVE: To compare live-birth rates between letrozole application and artificial cycle for endometrium preparation during frozen embryo transfer (FET) cycle among women with polycystic ovarian syndrome (PCOS). METHODS: A randomized controlled trial was conducted. Women with PCOS were randomized to letrozole application for ovulation induction compared with artificial cycle for endometrial preparation during FET. The primary outcome was live-birth rate per embryo transfer. Secondary outcomes included pregnancy-related outcomes, perinatal outcomes, and maternal complication rates. Assuming α=0.05 and 80% power, 186 patients per group were required to demonstrate a difference of 15% in live-birth rate: 205 patients (at least) per group were randomized to allow for a 10% dropout rate. RESULTS: Four hundred twenty patients were enrolled from 2018 to 2021. Two hundred ten patients were assigned to the letrozole application group, and 210 were assigned to the artificial cycle group. There was no difference in the live-birth rate (42.4% vs 42.9%, P =>.99). There was no difference in secondary outcomes, including clinical pregnancy rate (51.4% vs 56.2%, P =.378), implantation rate (51.8% vs 55.8%, P =.401), and miscarriage rate (8.6% vs 11.0%, P =.511). For perinatal outcomes, singleton birth weight was significantly higher in the artificial cycle group (3,108±56 g vs 3,301±58, P =.018), and the incidence of gestational diabetes mellitus (GDM) was significantly higher in letrozole application group (14.6% vs 5.6%, P =.050). The other outcome was no difference in maternal complications. CONCLUSION: There was no difference in pregnancy outcomes between letrozole application compared with artificial cycle for endometrial preparation in women with PCOS who underwent FET. The risk of GDM was higher in the letrozole application group, and the singleton birth weight was lower in the artificial cycle group. CLINICAL TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR1800014746.