The aim of the study was to compare the effect of clomiphene citrate (CC) and letrozole on endometrial receptivity for ovulation induction in women with polycystic ovary syndrome (PCOS). A randomized controlled study included 160 patients diagnosed with PCOS, out of which 80 patients received 50 mg of CC and 80 patients received 2.5 mg of letrozole for successful ovulation induction. Endometrial thickness and pattern, the blood flow of uterine artery and subendometrial region, endometrial volume and vascularization index were measured. The ratio of multilayered endometrial pattern in letrozole group was significantly increased on the day of human chorionic gonadotropin (hCG) administration compared with CC group (77.5% vs. 55.0%). The volume, vascularization index (VI), flow index (FI), and vascularization flow index (VFI) of endometrium on the day of hCG administration and 7-9 days after ovulation in letrozole group were significantly increased. The biochemical pregnancy rate, clinical pregnancy rate, and ongoing pregnancy rate in letrozole group were significantly increased compared with CC group (36.3%, 30.0%, 22.5% vs. 21.3%, 13.8%, 10.0%, respectively). Letrozole increased pregnancy rates by improving endometrial receptivity compared with CC in patients with PCOS.
Keywords: Polycystic ovary syndrome; clomiphene citrate; endometrial and subendometrial blood flows; endometrial receptivity; letrozole.