Alpha-fetoprotein (AFP) is the major fetal plasma protein. The concentration of AFP peaks in the fetal bloodstream at 2-3 g/l around 12-14 weeks of gestation and then falls. AFP passes into the maternal bloodstream where it may be detected by assay. Fetal malformations such as neural tube defects (seen in Down’s syndrome) elevate the maternal serum levels. Elevated AFP is seen most frequently in adults with germ cell tumors and hepatocellular carcinoma, but also in gastric, colon, biliary, pancreatic and lung cancers (~20% of patients).
Swiss-Prot Accession Number: P02771