['Uterine fibroid tumors have been associated with adverse outcomes in singleton pregnancies. We aimed to estimate risk for adverse obstetric outcomes that are associated with fibroid tumors in twin pregnancies.', 'A retrospective cohort study of twin pregnancies with ≥1 fibroid tumor on second trimester ultrasound examination. Outcomes included small-for-gestational-age fetal growth, preterm delivery, preterm rupture of membranes, abruption, preeclampsia, and intrauterine fetal death. Univariable and multivariable analyses were used to evaluate the impact of fibroid tumors on outcomes in twin pregnancies compared with twin pregnancies without fibroid tumors.', "Of 2378 nonanomalous twin pregnancies, 2.3% had fibroid tumors. Twin pregnancies with fibroid tumors were no more likely to have small-for-gestational-age growth (40.0% vs. 36.0%; adjusted odds ratio, 1.1; 95% confidence interval, 0.7-2.0) or preterm delivery at <34 weeks' gestation (25.0% vs. 24.0%; adjusted odds ratio, 1.0; 95% confidence interval, 0.5-1.9) than twin pregnancies without fibroid tumors. Other adverse outcomes were no more likely to occur in twin pregnancies with fibroid tumors than in twin pregnancies without fibroid tumors. Post hoc power calculations suggested >97% power to detect 2-fold differences in small for gestational age and preterm delivery at <34 weeks' gestation."] Are fibroid tumors a risk factor for adverse outcomes in twin pregnancies?