Intestinal obstruction, often atresia, presents in the first few days of life as bilious vomiting sometimes accompanied by abdominal distention and failure to pass meconium. Infants are often premature and small for gestational age and a prenatal diagnosis may be made in babies with polyhydramnios. Intestinal obstruction with bilious vomiting in neonates is caused by duodenal atresia, malrotation, volvulus, jejunoileal atresia, meconium ileus, and necrotizing enterocolitis. Babies with stenosis present as newborns or later with recurrent vomiting and failure to thrive.