OBJECTIVE To evaluate the pregnancy outcome after ovulation induction with aromatase inhibitors or clomiphene citrate (CC). METHODS A prospective, randomized, controlled trial. METHODS A university hospital center and a private practice setting. METHODS The study comprised a total of 796 infertile women (1,100 cycles) and 200 spontaneously pregnant women (298 cycles) as a control group. METHODS Patients were allocated treatment either with 100 mg of CC daily (420 patients, 634 cycles), 5 mg of letrozole daily (269 patients, 323 cycles) or 1 mg of anastrozole daily (107 patients, 143 cycles) for 5 days starting on day 3 of menses. METHODS The occurrence of pregnancy, miscarriage and neonatal condition. RESULTS Pregnancy occurred in 167/1,398 cycles (11.9%) in total without significant differences between groups. The total miscarriage rate was 16.1% (varied between 14.2% in CC group and 19.9% in anastrozole group) without difference between spontaneous and stimulated pregnancies. There were 129 deliveries in all groups. There were no significant differences between the stimulated and spontaneous pregnancies as regards mean gestational age, premature deliveries, birth weight, SGA<10th percentile or five minutes Apgar score. There was one case of complete cleft palate and one case of major congenital heart problem in the letrozole group. There were two cases of talipus equinovarus in the CC and spontaneous pregnancy group. CONCLUSIONS Aromatase inhibitors and CC resulted in favorable pregnancy outcomes and average miscarriage rates. Safety of the drugs for both the mother and fetuses was documented.