Effect of different timing of letrozole initiation on pregnancy outcome in polycystic ovary syndrome.

Objective: To investigate the efficacy of oral letrozole (LE) starting on day 3 or 5 of the menstrual cycle in patients with polycystic ovary syndrome (PCOS). Design: Retrospective cohort study. Setting: Reproductive Endocrinology Department of Hangzhou Women's Hospital. Methods: In this retrospective analysis, we analyzed patients who received oral LE for ovulation induction (OI) at the Hangzhou Women's Hospital from January 2016 to January 2021. In total, 539 PCOS patients with fertility requirements were classified into the D3 group and D5 group according to the different starting times of oral LE, that is, from the 3rd or 5th day of the menstrual cycle or LE is taken orally for 5 days starting on day 3 or 5 of progesterone withdrawal bleeding. Treatment started with one tablet (LE 2.5 mg), continue the regimen from the previous cycle in non-responders and continued until pregnancy or for up to three ovulatory cycles, with visits to determine ovulation and pregnancy, followed by tracking of pregnancies. The primary outcome was to compare ovulation rates, conception rates, live birth rates, pregnancy complications, and pregnancy outcomes at different initiation times. Results: Women who started LE on the 5th day of their menstrual cycle had more cumulative conception rates than those who started LE on the 3rd day(173 of 228[75.9%] Conclusion: As compared with D3 group, D5 group was associated with higher ovulation and conception rates, shorter time-to-pregnancy among infertile women with the PCOS.