Pregnancy outcome after the use of an aromatase inhibitor for ovarian stimulation.

OBJECTIVE: This study was undertaken to report the outcome of pregnancies achieved after ovarian stimulation, including the use of the aromatase inhibitor, letrozole, for ovarian stimulation.

STUDY DESIGN: A cohort study comparing the outcome of pregnancies achieved after letrozole and other ovarian stimulation treatments with a control group of pregnancies spontaneously conceived without ovarian stimulation.

RESULTS: In 3 tertiary referral centers, there were 394 pregnancy cycles in 345 infertile couples (63 pregnancies with 2.5 mg of letrozole alone or with gonadotropins, 70 pregnancies with 5.0 mg of letrozole, 113 pregnancies with clomiphene alone or with gonadotropins, 110 pregnancies with gonadotropins alone, and 38 pregnancies achieved without ovarian stimulation). Pregnancies conceived after letrozole treatments were associated with similar miscarriage and ectopic pregnancy rates compared with all other groups. In addition, letrozole use was associated with a significantly lower rate of multiple gestation compared with clomiphene citrate.

CONCLUSION: The favorable pregnancy outcome and low multiple gestation rate of aromatase inhibitors for ovarian stimulation is encouraging for the development of these agents as first-line ovulation induction agents.