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,
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
nonpregnant women, and children, AFP in the blood can mean that certain types of
cancer—especially cancer of the
pancreas, or liver—are present. High levels of AFP may
also be found in
lymphoma, brain tumors, and renal cell cancer.