This is a protein the blood level of which is measured by laboratory methods. Its level is elevated in the mother's blood when there are fetal spinal cord defects (anencephaly, myelomeningocele), threatened abortion, twin gestation, and abruptio placentae. The AFP screening test for the mother's blood is usually conducted at 16 - 18 weeks of pregnancy. AFP level in the amniotic fluid obtained in amniocentesis is measured to identify abnormal fetal development. In humans, AFP is a useful marker for the diagnosis and assessment of the tumors of the testis (teratocarcinoma and embryonal carcinoma). AFP is also elevated in patients with primary liver cancer (hepatocellular carcinoma) and in women with some types of germ cell ovarian tumors. Normal range: less than 40 micrograms per liter.