Alpha-fetoprotein (AFP) is the most predominant plasma protein produced by the yolk sac and liver during embryonic development. After birth, its concentration in the plasma rapidly decreases, but it starts declining during the last 3 months of pregnancy. It usually reaches normal adult levels around 8-12 months after birth. The measurement of AFP levels in maternal blood or amniotic fluid is used for screening and detecting abnormal fetal development. AFP levels can be elevated in certain conditions, including umbilical hernia, primary hepatocellular carcinoma, neural tube defects, non-seminomatous germ cell tumors, yolk sac tumors, and cerebellar ataxia telangiectasia.