Effect of differential endometrial injury timing on frozen-thawed embryo transfer pregnancy outcomes

Objective: To explore whether differential endometrial injury (El) timing prior to a frozen-thawed embryo transfer (FET) cycle yields similar improvements in pregnancy outcomes. Materials and Methods: A total of 688 women underwent consecutive FET cycles. Based on their desire to undergo differentially timed Et or not, patients were divided into four groups: on the 3rd-5th day of the menstnial phase of the FET cycle (n = 308), on the 3rd-5th day of the menstrual phase preceding the FET cycle (n 78), during the luteal phase of the cycle preceding the FET cycle (n = 83), and no intervention (n = 219). Results: The pregnancy outcomes in the four groups were significantly different. The chemical pregnancy, clinical pregnancy, implantation, and live birth rates of patients who underwent Et on the 3rd-5th day of the menstrual phase preceding the FET cycle were the highest, followed by those who underwent El on the 3d-5th day of the menstrual phase of the FET cycle. The lowest rates were those during the luteal phase of the cycle preceding the FET cycle and patients who had no interventions, which were similar. Conclusions: Differential Et timing resulted in differential improvement of pregnancy outcomes for FET.