Congenital abdominal wall defects, frequently associated with other anomalies, are found in many forms. Consequently, there is still controversy in the literature concerning nomenclature, classification, and pathogenesis. Recently, we proposed a new nomenclature and classification of abdominal wall defects based on the early development of the umbilical cord and of the ventral body wall. According to this classification the complete spectrum of abdominal wall defects, including cloacal exstrophy, bladder exstrophy, and epispadias, can be subdivided into four types: primary (thoraco-)abdominoschisis, omphalocele, body wall dysplasia, and secondary (thoraco-)abdominoschisis. Each type is characterized by its specific configuration of the placenta, the membranes, the umbilical cord, and the fetus. Anomalies such as urachal remnants and omphalomesenteric duct malformations can be explained by disturbances during later stages of umbilical cord development.