Clomiphene citrate or aromatase inhibitors for superovulation in women with unexplained infertility undergoing intrauterine insemination: a prospective randomized trial

ObjectiveTo compare clomiphene citrate (CC) and letrozole used for superovulation before intrauterine insemination (IUI) in unexplained infertility.DesignProspective randomized trial.SettingA university teaching hospital and a private practice setting.Patient(s)Four hundred and twelve infertile women with unexplained infertility.Intervention(s)Patients were randomized to treatment with 100 mg of CC daily (207 patients, 404 cycles) or 5 mg of letrozole daily (205 patients, 400 cycles) for 5 days starting on day 3 of menses. The IUI was done 36 ± 4 hours after human chorionic gonadotropin (hCG) injection.Main Outcome Measure(s)Number of follicles, serum estradiol level, serum progesterone level, endometrial thickness, and pregnancy and miscarriage rates.Result(s)The total number of follicles during stimulation was statistically significantly greater in the CC group (3.1 ± 0.36 vs. 1.6 ± 0.41). There was no statistically significant difference in pretreatment endometrial thickness between the two groups or endometrial thickness at the time of hCG administration. Serum E2 and progesterone concentrations were statistically significantly higher in the CC group. The days to hCG injection were similar in both groups. Pregnancy occurred in 73 out of 205 patients (400 cycles) in the letrozole group (35.6% and 18.2%, respectively) and 78 out of 207 patients (404 cycles) (37.6% and 19.3%, respectively) in the CC group; the differences were not statistically significant. Two twin pregnancies occurred in the CC group.Conclusion(s)This study found no superiority between letrozole and CC for inducing ovulation in women with unexplained infertility before IUI.