Perinatal outcomes and congenital anomalies associated with letrozole and natural cycles in single fresh cleaved embryo transfers: A single-center, 10-year cohort study

OBJECTIVE: To investigate and compare the safety of letrozole and natural cycles in fresh early embryo transfers. DESIGN: A retrospective cohort study. SETTING: A large fertility treatment center. PATIENT(S): Women who underwent natural and letrozole cycles during fresh early embryo transfer at Kato Ladies Clinic between January 2008 and December 2017. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Perinatal complications and congenital anomalies. RESULT(S): No significant differences were observed in pregnancy complications, gestational age, birth weight, small for gestational age, large for gestational age, and congenital anomalies between the the women who underwent natural and letrozole cycles. CONCLUSION(S): The perinatal outcomes and congenital anomaly rates associated with letrozole and natural cycles in fresh early embryo transfers were comparable. Therefore, our data support the safe use of letrozole in fresh early embryo transfers in assisted reproductive technology.