P-109 Letrozole versus hormone replacement therapy for frozen embryo transfer: A randomized clinical trial

Abstract Study question Do the outcomes of frozen embryo transfer cycles differ according to endometrial preparation (EP) with letrozole versus hormone replacement therapy (HRT)? Summary answer Letrozole seems be as effective HRT in terms treatment outcomes. What is known already Vitrification improved survival vitrified-warmed embryos and increased number FET cycles. A common EP strategy for includes augmentation endometrium using estrogen followed by progesterone supplements. Retrospective studies have shown that aromatase inhibitors (letrozole) was associated higher clinical pregnancy live birth rates, a lower miscarriage rate, compared maintains regular feedback mechanisms, facilitating normal follicular growth, promotes single follicle development ovulation. Moreover, it does not any negative effects on can improve receptivity. design, size, duration This randomized controlled trial performed two university-affiliated medical centers. total 170 patients undergoing from June 2018 2021 were eligible. Participants/materials, setting, methods Patients either (n = 69) or protocol 101) EP, blocked randomization method. Inclusion criteria blastocyst uterine cavity. Exclusion older than 40 years, oocyte donation cycles, more 3 previous transfers without pregnancy. The primary study outcome percentage pregnancies, defined pregnancies/embryo transfers, excluding canceled treatments. Main results role chance characteristics groups comparable age, BMI, gravidity, parity, history relevant fresh cycle which frozen. After 5 cancelled treatments group 2 group, pregnancies between arms similar (24 (38.0%) 34 (34.6%), respectively, p 0.67). There no difference percentages births (22 (34.9%) 28 (28.6%), 0.4) missed abortions (1 (4.1%) (14.7%), 0.19). For who did achieve cycle, we retrospectively examined next other protocol, when possible. Achievement same change both (7(50%) 9(50%) group). Limitations, reasons caution Limitations this included heterogeneous groups. Even though class II ovulation disorders prevalence groups, they different indications ART. Pregnancy complications evaluated should further investigated larger sample size. Wider implications findings possible advantages fewer complications. could suitable option and, enables convenient timing, natural FET. Trial registration NCT03540979