Gastrointestinal tract and internal abdominal wall malformations are infrequent malformations. Their global incidence is estimated to be below three to six cases in every 1,000 newborns, although it is probably higher, since many of them are part of very severe multiple malformations syndromes, with a high incidence of intrauterine death even in early stages of pregnancy. They are often associated with polyhydramnios, which is in 10% associated with upper digestive atresias, and in another 10% with lower digestive atresias. Colon atresia is responsible of 5–10% of all the intestinal atresias with most frequent anal atresia occurring in around 1 in every 5,000 live births. Many other fetal intestinal disorders have been described by ultrasound including small intestine or anorectal atresia, Hirschsprung's disease, megacolon with anourethral atresia, and distended and descended colon, which is associated with Johanson–Blizzard syndrome. It is important to diagnose possible malformations in other organs and systems that may be related to these defects and therefore, will determine the neonatal prognosis. These anomalies are diagnosed by two-dimensional (2D) ultrasound assessment, many of them even in the first trimester, but three-dimensional (3D) and four-dimensional (4D) ultrasound is a remarkable advance in a better definition of the defect.