Comparison of the Effects of Letrozole and Clomiphene Citrate on Ovulation and Pregnancy Rate in Patients with Polycystic Ovary Syndrome

Background: For more than four decades clomiphene citratehas been the first line of the treatment for ovulatory disorders.The aim of this study was to compare the effects of letrozoleand clomiphene citrate on ovulation and pregnancy rate in patientswith polycystic ovary syndrome.Methods: In this prospective double-blind study, 100 patientswith polycystic ovary syndrome were randomized into twoequal groups. The first group received letrozole, 5mg daily(per oral) and the second group received clomiphene, 100mgdaily during the 3rd-7th days of the menstrual cycles. Intramuscularhuman chorionic gonadotropin (hCG) (10,000 IU)was administered to trigger ovulation when at least one maturefollicle (≥ 18mm) was developed.Results: Ovulation occurred in 30 patients (60%) of the letrozolegroup and in 16 patients (32%) of the clomiphene group,which showed a statistically significant difference (P=0.009).The mean number of follicles with diameter >14 mm on theday of administration of hCG was 1.06±0.95 in the letrozolegroup and 1.14±1.17 in the clomiphene group, which showednon-significant difference (P=0.962).No difference was found in the endometrial thicknessbetween the two groups. A non-significant increase inpregnancy rate was observed in the letrozole group (26% v14% P=0.21).Conclusion: Ovulation rate was higher in letrozole group andadministration of letrozole was associated with a nonsignificantincrease in pregnancy rate.