The limitations of ultrasonography in the antenatal diagnosis of congenital cerebral malformations.

Ultrasonography is widely used in the antenatal diagnosis of neural tube defects. A case of holoprosencephaly associated with trisomy 18 is presented to illustrate the limitations of ultrasonography in making antenatal diagnosis of cerebral malformations. The use of a better organ-imaging technique, such as nuclear magnetic resonance, is suggested.