Alpha-Fetoprotein (AFP) in Blood
An alpha-fetoprotein (AFP) blood test checks the level of AFP in a pregnant woman's blood. AFP is a substance made in the liver of an unborn baby (fetus). The amount of AFP in the blood of a pregnant woman can help see whether the baby may have such problems as spina bifida and anencephaly. An AFP test can also be done as part of a screening test to find other chromosomal problems, such as Down syndrome (trisomy 21) or Edwards syndrome (trisomy 18). An AFP test can help find an omphalocele, a congenital problem in which some of the baby's intestines stick out through the belly wall.
Normally, low levels of AFP can be found in the blood of a pregnant woman. No AFP (or only a very low level) is generally found in the blood of healthy men or healthy, nonpregnant women.
The level of AFP in the blood is used in a maternal serum triple or quadruple screening test. Generally done between 15 and 20 weeks, these tests check the levels of three or four substances in a pregnant woman's blood. The triple screen checks alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and a type of estrogen (unconjugated estriol, or uE3). The quad screen checks these substances and the level of the hormone inhibin A. The levels of these substances-along with a woman's age and other factors-help the doctor estimate the chance that the baby may have certain problems or birth defects.
Screening tests are used to see what the chance is that your baby has a certain birth defect. If a screening test is positive, it means that your baby is more likely to have that birth defect and your doctor may want you to have a diagnostic test to make sure.
- Pregnancy: Should I Have Screening Tests for Birth Defects?
Men, nonpregnant women, and children
In men, nonpregnant women, and children, AFP in the blood can mean that certain types of cancer-especially cancer of the testicles, ovaries, stomach, pancreas, or liver-are present. High levels of AFP may also be found in Hodgkin's disease, lymphoma, brain tumors, and renal cell cancer.