Alpha-fetoprotein (AFP) is a protein produced primarily by the liver of a developing fetus. It plays a crucial role in fetal development, helping to transport nutrients and prevent the mother's immune system from rejecting the fetus. AFP levels are typically high during pregnancy but decrease significantly after birth. In adults, elevated levels of AFP can indicate certain health conditions, such as liver disease or specific types of cancer, including hepatocellular carcinoma. Doctors often measure AFP levels through a blood test to help diagnose or monitor these conditions, making it an important biomarker in medical practice.