Anatomic uterine defects appear to predispose women to reproductive difficulties, including first- and second-trimester pregnancy losses, higher rates of preterm labor and birth, and abnormal fetal presentation. These anatomic abnormalities can be classified as congenital, including müllerian and diethylstilbestrol-related abnormalities, or acquired, such as intrauterine adhesions or leiomyomata. In women with three or more consecutive spontaneous abortions who underwent hysterosalpingography or hysteroscopic examination of their uteri, mullerian anomalies have been found in 8 to 10%. Women with mullerian anomalies may be predisposed to recurrent pregnancy loss because of inadequate vascularity to the developing embryo and placenta, reduced intraluminal volume, or cervical incompetence. The reproductive history of most women with a müllerian anomaly is poor, especially for women with a uterine septum, the most common mullerian anomaly. Recurrent pregnancy losses resulting from a uterine septum, bicornuate uterus, intrauterine adhesions, and fibroids are amenable to surgical correction. Women with müllerian anomaly and a history of second-trimester pregnancy losses may benefit from a prophylactic cervical cerclage.