Is letrozole superior to clomiphene for ovarian stimulation prior to intrauterine insemination?

OBJECTIVE: To compare the efficacy of letrozole with clomiphene citrate for ovarian stimulation prior to intrauterine insemination. METHODS: A total of 272 patients underwent 362 cycles of stimulation prior to IUI from January 2009 to May 2011. One hundred and twenty-six patients (170 cycles) received letrozole 5 mg and 146 patients (192 cycles) received clomiphene citrate 100 mg for 5 days starting on day 3 of the cycle. Intrauterine insemination was done 36 ± 4 h after hCG injection in 99 patients (131 cycles) in the letrozole group and 115 patients (136 cycles) in the clomiphene group. The number of mature follicles and serum E2 levels was monitored on the day of hCG. Endometrial thickness was noted on the day of hCG and IUI as well. The pregnancy rate, the miscarriage rate, and other parameters were evaluated only for patients who underwent IUI. RESULTS: The mean number of mature follicles was significantly more in the clomiphene group (1.66 ± 1.69 vs. 1.41 ± 1.53) than in the letrozole group. No significant difference in endometrial thickness on the day of hCG administration was found; however, endometrial thickness was statistically significantly higher in the clomiphene group on the day of IUI (9.28 ± 1.43 vs. 8.77 ± 1.34). Serum E(2) levels on the day of hCG were statistically significantly higher in the clomiphene group (501.09 ± 2.45 vs. 214.79 ± 2.43 pg/ml). Pregnancy rate was 9.2 %/cycle and 12.12 %/patient in the letrozole group, and 8.1 %/cycle and 9.5 %/cycle in the clomiphene group; these differences were not statistically significant. CONCLUSION: This study found no superiority of letrozole over clomiphene when used for ovarian stimulation and IUI.