Clomiphene citrate or aromatase inhibitors combined with gonadotropins for superovulation in women undergoing intrauterine insemination: a prospective randomised trial.

The objective of this study was to test the use of letrozole in combination with follicle-stimulating hormone (FSH) vs clomiphene citrate (CC) with FSH for ovarian hyperstimulation prior to intrauterine insemination (IUI). A prospective randomised trial in which 280 women with unexplained infertility were randomised to 100 mg of CC (141 patients, 219 cycles) or 5 mg of letrozole daily (139 patients, 215 cycles) for 5 days starting on day 3 of menses both combined with gonadotropins for ovarian stimulation prior to IUI. The primary outcome measures were the number of growing and mature follicles, the concentrations of serum E2 (pg/ml) and progesterone (ng/ml), and the endometrial thickness (mm). The secondary outcome measure was the occurrence of pregnancy and miscarriage. The total number of follicles was significantly greater in the CC group (4.1 +/- 0.46 vs 2.6 +/- 0.43). There was no significant difference in endometrial thickness between the two groups. Pregnancy occurred in 33 out of 139 patients (215 cycles) in the letrozole group (23.7% and 15.3%, respectively) and 37 out of 141 patients (219 cycles) (26.2% and 16.8%, respectively) in the CC group; the differences were not statistically significant. The allied use of either CC or letrozole, during ovarian stimulation to reduce the dose of gonadotropins prior to IUI is justified. This approach will reduce the cost of stimulation protocols without effect on the treatment outcome and letrozole has no advantage over CC in this respect.