Monozygotic twins discordant for body stalk anomaly.

We report on two cases of monozygotic twins discordant for body stalk anomaly, diagnosed prenatally in a multicenter ultrasound screening study at 10-14 weeks of gestation. Ultrasound showed a large abdominal wall defect with most of the abdominal contents and almost half of the body in the celomic cavity, in association with severe kyphoscoliosis and a very short umbilical cord. Both pregnancies were managed expectantly and delivered by Cesarean section. The abnormal babies died soon after birth and autopsy confirmed the sonographic diagnosis. Body stalk anomaly in twins is extremely rare. These are, to our knowledge, the first cases reported on monozygotic twins discordant for this anomaly, indicating that the incomplete twinning theory cannot uniformly explain the pathogenesis of the body stalk in twins.