Impact of letrozole on ultrasonographic markers of endometrial receptivity in polycystic ovary syndrome women with poor endometrial response to clomiphene citrate despite adequate ovulation

ObjectivesTo investigate the endometrial effects of letrozole in PCOS women with poor endometrial response (endometrium thickness ⩽7 mm) to clomiphene citrate (CC) despite adequate ovulation, using the ultrasonographic markers of endometrial receptivity.Study designAmbidirectional cohort study.Patients and methodsSixty 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.ResultsIn 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 < 0.05) and rate of detection of subendometrial blood flow. Both RI and PI of spiral arteries in the letrozole cycle (0.63 ± 0.05 and 1.12 ± 0.06, respectively) showed significantly lower impedance compared to the previous CC cycle (0.75 ± 0.09 and 1.42 ± 0.13, respectively) (P < 0.05). Pregnancy rate per cycle was 20% (12/60) in the letrozole cycle, all in women with endometrial thickness ⩾7 mm.ConclusionLetrozole is an effective second-line treatment in women with inadequate endometrial response to CC, as letrozole increased endometrial thickness trilaminar pattern and improved endometrial perfusion.