Prenatal diagnosis of alobar holoprosencephaly at 10 weeks of gestation.

Alobar holoprosencephaly is an intracranial abnormality characterized by failure of proper cleavage of the prosencephalon, accompanied by incomplete midfacial development. The prenatal sonographic diagnosis of alobar holoprosencephaly was first described in 1984; however, there have been only two reports of alobar holoprosencephaly diagnosed in the first trimester. We report a case of alobar holoprosencephaly diagnosed at 10 weeks of gestation.