Comparison of the success rate of letrozole and clomiphene citrate in women undergoing intrauterine insemination

This study was conducted to compare the success rate of daily administration of aromatase inhibitor letrozole at a dose of 5 mg when administrating clomiphene citrate (CC) 100 mg daily in women undergoing superovulation and IUI. This prospective randomized trial was done in Research and Clinical Center for Infertility (Shahid Sadoughi University), Yazd, Iran. Ninety-five patients with unexplained and mild male factor infertility were studied. Using a computer-generated random table, the patients were randomized into two groups, which were treated with 5 mg of letrozole daily (42 patients, 42 cycles) or 100 mg of CC daily (53 patients, 53 cycles). The data were analyzed using Student''s t-test and chi square test. The mean age and duration of infertility in both groups were similar. There was a significant difference between the two groups in the total numbers of follicles during stimulation (5.45 ± 4.2 in CC group vs. 3.07 ± 2.1 in letrozole group) (P = 0.01). No significant difference in the endometrial thickness was found between the two groups (letrozole group = 6.9 ± 2.2, CC group = 7.8 ± 1.8). The mean levels of LH and FSH in both groups were similar. P value of difference in hormone levels between two groups were 0.33 and 0.47, respectively, but there was a significant difference in mean E2 levels between the two groups (241.28 ± 167.537 in letrozole group vs. 867.34 ± 296.689 in CC group) (P = 0.018). The mean number of gonadotropin ampules used in both groups was the same. Pregnancy rate per cycle was 9.5% in the letrozole group and 5.7% in the CC group (P = 0.6). Two out of the three pregnancies in the CC group (66.6%) and one out of the four pregnancies in the letrozole group resulted in a miscarriage (25%). One twin pregnancy (33%) occurred in the letrozole group and none in the CC group. Ovarian hyperstimulation syndrome (OHSS) did not occur in either of the two groups. In IUI, superovulation with clomiphene citrate and letrozole was associated with similar pregnancy rates, but the miscarriage rate was higher with clomiphene citrate.