The term given to the condition in which a child is born with a defect of the skull and absence of the cerebral hemispheres; the brain stem and cerebellum are also atrophic. It has an incidence of 0·65 per 1,000 live births. Miscarriage (or therapeutic abortion) are common but if the pregnancy goes to term the infants do not live very long. It is possible to detect the presence of anencephaly in the fetus by measuring the level of ALPHA-FETO PROTEIN in the mother's serum or in the amniotic fluid. (See also SPINA BIFIDA.)