α-Fetoprotein (AFP) belongs to the α1-globulin family of human plasma proteins and contains approximately 4% carbohydrate. AFP is produced primarily in the fetal liver and can be found in fetal and maternal blood and in amniotic fluid.
As part of a quad-marker screening protocol with human chorionic gonadotropin, unconjugated estriol, and Inhibin A, immunoassays for maternal serum levels of AFP are useful in detecting neural tube defects and Down's Syndrome. Elevated AFP serum levels are also found in pregnant women with diabetes and Rh immunization. Furthermore, AFP serum levels may be indicative of viral hepatitis, chronic active hepatitis, ulcerative cholitis, Crohn's disease, alcoholic cirrhosis, and adenocarcinoma of the liver, lung, pancreas, stomach, and gall bladder.