Effect of baseline ovarian cysts on in vitro fertilization and gamete intrafallopian transfer cycles. The presence of ovarian cysts may compromise the success of in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT). We prospectively studied 212 consecutive ovulation induction cycles in 120 patients for IVF and/or GIFT. A baseline cyst was defined as any intraovarian cystic structure greater than or equal to 12 mm noted on ultrasonography before superovulation. Cycle outcomes were compared between patients with cysts (n = 62) versus those with no cysts (n = 150). There were no differences in follicular or luteal phase lengths or amount of human menopausal gonadotropins used. Peak estradiol (E2) levels were significantly lower and cancellation rates significantly higher in the cyst group. For noncanceled cycles, there were no significant differences in peak E2 levels, the mean number of follicles greater than or equal to 12 mm, mature oocytes retrieved, or ova transferred for GIFT or embryos for IVF. The pregnancy rates overall and for noncanceled cycles were not significantly different. 