Predictors and characteristics of letrozole induced ovulation in comparison with clomiphene induced ovulation in anovulatory PCOS women

To evaluate predictors and characteristics of letrozole induced ovulation in comparison with clomiphene induced ovulation in a group of PCOS women. Prospective randomized controlled double blind trial. Infertility unit of university hospital. 124 PCOS patients undergoing ovulation induction for one cycle using either clomiphene or letrozole. 100mg of CC/day for 5 days or 5 mg of Letrozole/day for the same duration starting within 5 days of progestin induced withdrawal bleeding. Ovulation rate, number of follicles, final endometrial thickness, mid-luteal progesterone, and pregnancy. Comparable ovulation and pregnancy rates were obtained with clomiphene and letrozole. Endometrium at ⩾18 mm follicle diameter was significantly thinner and mid luteal progesterone was significantly lower in clomiphene group. Within each group there was no significant difference in any of the baseline variables between responders and non-responders. High basal LH was associated with non-response in the whole study population. Letrozole is at least as good as CC in inducing ovulation and achieving pregnancy in PCOS cases. Serum progesterone and endometrium were significantly more favorable with letrozole. High basal LH correlated with failure in both groups.