Two- and three-dimensional prenatal sonographic diagnosis of Alagille syndrome.

We describe a case of Alagille syndrome diagnosed by second-trimester ultrasound. Features included the characteristic prominent chin, single umbilical artery, and hemivertebrae. Three-dimensional imaging demonstrated classic butterfly vertebrae, which were not otherwise appreciable. Alagille syndrome may be detected by second-trimester ultrasound in the at-risk fetus.