Anencephaly is a lethal birth defect characterized by the absence of all or part of the skull and scalp and malformation of the brain.
As an isolated defect, anencephaly appears to be caused by a combination of genetic factors and environmental influences that predispose to faulty formation of the nervous system.
Anencephaly is readily apparent at birth because of exposure of all or part of the brain. Not only is the brain malformed, but it is also damaged because of the absence of the overlying protective encasement.
Anencephaly is a rare and severe neural tube defect that occurs in about 1 in 4,859 births in the United States. It affects all racial and ethnic groups, although some studies have suggested higher rates among Hispanic women. The condition more commonly affects females than males.