Protein coded by the AFP gene and produced by fetal tissues, an abnormally high amount of which in the amniotic fluid or maternal serum may indicate a neural tube defect, or some other loss of structural integrity in the fetus.
Source: PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 719 (https://doi.org/10.1515/pac-2015-1202)