Reliable criteria for the prenatal sonographic diagnosis of alobar holoprosencephaly.

A series of 10 consecutive cases of alobar holoprosencephaly is described. The disorder was diagnosed prenatally by ultrasound according to two criteria: a large central fluid collection in the fetal head, with no visible midline structures but with the presence of a mantle around the fluid collection and fusion of the thalami and corpus striatum, and sonographic abnormalities of the face, including hypotelorism, central clefts, facial asymmetry, and abnormal orbits.