Objectives: To investigate the endometrial effects of letrozole in PCOS women with
poor endometrial response (endometrium thickness 67 mm) to clomiphene citrate (CC) despite adequate
ovulation, using the ultrasonographic markers of endometrial receptivity.
Study design: Ambidirectional cohort study.
Patients and methods: Sixty women with anovulatory PCOS having endometrial thickness less
than 7 mm despite adequate ovulation with CC underwent ovulation induction with Letrozole
(5 mg/day from cycle day 3 to 7) for one treatment cycle. Main outcome measures: Comparison
of the endometrial thickness (ET) and pattern, uterine artery and spiral artery, resistance index
(RI) and pulsatility index (PI) between the current letrozole and previous CC stimulated cycles.
Results: In the current letrozole cycle compared with the previous CC cycles, there were significantly
greater midcycle endometrial thickness (8.97 ± 1.32 vs. 5.7± 1.2, respectively; P < 0.05),
multilayered endometrial pattern (93.33% vs. 50%, respectively; P