Gastroschisis is a congenital defect of the abdominal wall that occurs laterally to, and often to the right of, a normally closed umbilical ring. Visceral organs that herniate through the defect are not covered by a membrane. Gastroschisis is distinct from omphalocele (164750), which is characterized by herniation of abdominal contents through the base of the umbilical cord; in omphalocele, the visceral organs are covered by membranes (summary by Mastroiacovo et al., 2007). Both omphalocele and gastroschisis, when they occur without other malformations, are probably multifactorial (Baird and MacDonald, 1981).