RESUMO
AIM: To compare cycle properties of ovulation induction (OI) with gonadotropin alone or combined with letrozole in the patients with previous clomiphene citrate (CC) failure. METHODS: In this prospective study, 40 patients with previous at least three times CC cycle failure were evaluated. Half of them received 2.5 mg letrozole on days 3-7 of the menstrual cycle and recombinant follicle stimulating hormone (rFSH) starting on day 5. The other half of the patients received only rFSH starting on day 3. Groups were compared according to the OI duration, gonadotropin dosage, endometrial thickness, estradiol (E2) levels on day of human chorionic gonadotropin (HCG) administration and follicle count. RESULTS: Total rFSH dose, the E2 levels on the day of HCG and >18 mm follicle count was significantly lower and OI duration was significantly shorter in rFSH + letrozole group. Mean endometrial thickness was not different between groups. CONCLUSION: Adding letrozole to gonadotropin in OI cycles decreases total gonadotropin dose and induction duration without any adverse effects on endometrial thickness. Monoovulation is better achieved by adding letrozole to gonadotropin stimulation without decreasing pregnancy rates.