What is the primary source of serum alpha-fetoprotein during pregnancy?

The primary source of serum alpha-fetoprotein (AFP) during pregnancy is the fetal liver. AFP is a protein produced by the fetal yolk sac early in pregnancy, but as the pregnancy progresses, the fetal liver becomes the main site for its production, typically around the second trimester.

As the fetus develops, AFP levels in the maternal serum can serve as an important indicator for various conditions, including neural tube defects and certain fetal anomalies. The fetal liver's role in AFP synthesis is critical to the proper function of this protein during gestation, as it reflects the health and development of the fetus.

Other sources, such as the maternal liver or the placenta, do not primarily produce AFP during pregnancy. While the placenta plays important roles in hormone production and fetal-maternal exchange, it does not significantly contribute to the levels of AFP in maternal serum. Likewise, the fetal neural tube does not produce AFP; it is actually more directly involved in developmental processes rather than protein synthesis for maternal circulation. Understanding the roles of these different organs is key in grasping the clinical significance of AFP testing in prenatal care.