What is an alpha-fetoprotein (AFP) test?Alpha-fetoprotein (AFP) is a protein produced in the liver of a developing fetus. During a baby's development, some AFP passes through the placenta and into the mother's blood. An AFP test measures the level of AFP in pregnant women during the second trimester of pregnancy. Too much or too little AFP in a mother's blood may be sign of a birth defect or other condition. These include:A neural tube defect, a serious condition that causes abnormal development of a developing baby's brain and/or spineDown syndrome, a genetic disorder that causes intellectual disabilities and developmental delaysTwins or multiple births, because more than one baby is producing AFPMiscalculation of due date, because AFP levels change during pregnancyOther names: AFP Maternal; Maternal Serum AFP; msAFP screen
