Use of letrozole versus clomiphene citrate combined with gonadotropins in intrauterine insemination cycles: a pilot study

Objective: To compare the clinical outcomes between letrozole and clomiphene citrate (CC) in gonadotropin-combined intrauterine insemination (IUI) study. Design: Prospective pilot study. Setting: One university hospital and two private infertility clinics. Patient(s): Ninety-three infertile couples eligible for superovulation and IUI. Intervention(s): A letrozole dose of 2.5 mg/day (n = 66) or a CC dose of 100 mg/day (n = 27) was given on day 3-7 of the menstral cycle, combined with human menopausal gonadotropin (hMG) at a dose 150 IU every other day starting on day 5. Main Outcome Measures(s): The number of mature follicles, serum estradiol (E-2) and progesterone (P) levels, endometriel thicknesses on the day of human chorionic gonadotropin (hCG), and clinical pregnancy rates. Result(s): The patients' clinical characteristics were comparable between the two groups. The number of mature follicles (3.2 +/- 1.7 vs. 5.6 +/- 2.4) and serum E-2 levels on the day of hCG (231.0 +/- 179.8) vs. 1,371.7 +/- 750.5 PG/mL) were significantly lower in the letrozole group. No significant differences were in endometrial thickness measured on the day of hCG or clinical pregnancy rates (18.2% vs. 25.9%). The rate of patients with serum P levels > 1.0 ng/mL on the day of hCG was significantly lower in the letrozole group (4.5% vs. 25.9%). Conclusion(s): Letrozole produced a comparable pregnancy rate vs. CC in gonadotropin-combined IUI cycles. Our results should be confirmed in larger populations with proper randomization.