Why alpha-fetoprotein is elevated in maternal blood in neural tube defects?

Alpha-fetoprotein (AFP) is a protein produced by the fetal liver, and its levels can be elevated in maternal blood when neural tube defects (NTDs) are present. This elevation occurs because NTDs, such as spina bifida or anencephaly, allow AFP to leak into the amniotic fluid and subsequently into the maternal circulation. The increased presence of AFP in maternal blood serves as a potential biomarker for detecting these fetal abnormalities during pregnancy. Thus, elevated AFP levels can indicate a higher risk of NTDs, prompting further diagnostic investigations.