Antigen that occurs naturally in the fetus and sometimes in adults with certain cancers. A greater-than-normal amount of alpha fetoprotein (AFP) in the fetus often indicates an abnormality of the neural tube (e.g., hydrocephalus or spina bifida).
An antigen present in the human fetus and in certain pathological conditions in adults. The amniotic fluid level can be used to evaluate fetal development. Elevated serum levels are found in adults with certain kinds of liver diseases.