Objective: To estimate the risk of adverse pregnancy outcomes associated with the presence of leiomyomas. Methods: This was a retrospective cohort study of all consecutive singleton pregnancies from 1990 to 2007 undergoing routine second-trimester fetal anatomic ultrasound survey. The presence or absence of leiomyomas was noted at second-trimester ultrasound examination. Primary and secondary obstetric outcomes were obtained as the individual progressed to delivery. Women with at least one leiomyoma at the time of second-trimester anatomic survey were compared with women without leiomyomas. Primary outcomes were intrauterine fetal death, breech presentation, placenta previa, cesarean delivery, placental abruption, preeclampsia, intrauterine fetal growth restriction, preterm premature rupture of membranes, and preterm birth. Univariable and multivariable analyses were performed. Results: Of 72,373 women who underwent routine second-trimester anatomic survey, 64,047 women had complete obstetric follow-up data. The incidence of leiomyomas was 3.2% (n=2,058). Breech presentation (5.3% compared with 3.1%, adjusted odds ratio [OR] 1.5, 95% confidence interval [CI]1.3-1.9), placenta previa (1.4% compared with 0.5%, adjusted OR 2.2, 95% CI 1.5-3.2), cesarean delivery (33.1% compared with 24.2%, adjusted OR 1.2, 95% CI 1.1-1.4), placental abruption (1.4% compared with 0.7%, adjusted OR 2.1, 95% CI 1.4-3.0), preterm premature rupture of membranes (3.3% compared with 2.4%, adjusted OR 1.3, 95% CI 1.0-1.7), preterm birth less than 37 weeks (15.1% compared with 10.5%, adjusted OR 1.5, 95% CI 1.3-1.8), and less than 34 weeks (3.9% compared with 2.8%, adjusted OR 1.4, 95% CI 1.0-1.8), and intrauterine fetal death in women with a fetus with growth restriction (3.9% compared with 1.5%, adjusted OR 2.5, 95% CI 1.2-5.0) were significantly associated with the presence of leiomyomas. Conclusion: Women with leiomyomas are at low risk for obstetric complications compared with women without leiomyomas.