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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 gastroschisis, 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.
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.
Health Tools help you make wise health decisions or take action to improve your health.
The AFP test is done to:
You do not need to do anything before
you have this test.
If you are pregnant, you will be weighed
before the blood test, because the test results will be based on your weight.
The test results are also based on race, age, and how many weeks you are in your
The health professional drawing blood
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
You may feel anxious while awaiting results of an
alpha-fetoprotein test done to determine the health of your unborn baby.
There is very little chance of a problem from
having blood sample taken from a vein.
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 a developing baby (fetus). The amount of AFP in the blood
of a pregnant woman can help find certain problems with her baby.
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, normal values vary with the age of the baby. A high or low AFP may mean
that the age of the baby has been recorded wrong or not calculated correctly.
ultrasound may be done to check the baby's age more
0-40 nanograms per milliliter (ng/mL) or micrograms per liter (mcg/L)footnote 2
10-150 ng/mL or mcg/Lfootnote 3
In pregnant women, the amount of AFP gradually rises
starting in the 14th week of pregnancy. It continues to rise until a month or
two before giving birth, then it slowly decreases. Values are generally
slightly higher for black women than they are for white women. Values are
slightly lower for Asian women than they are for white women. An accurate
estimate of the age of the baby is needed to understand the AFP value
The normal range of AFP values is adjusted for each
woman's age, weight, and race; whether she has
diabetes that needs injections of
insulin; and the age of her baby (gestational age). If
the age of the baby is changed after an ultrasound, the AFP must then be
adjusted as well. Each woman and her doctor need to look at the range of
AFP values that is normal for her when she has an AFP test.
A normal AFP result does not guarantee a normal pregnancy or
In a pregnant woman, a low level of
alpha-fetoprotein can mean:
In a nonpregnant adult, alpha-fetoprotein is not
AFP test results can be abnormal,
even when nothing is wrong with the baby.
Things that may affect the
results of your test include:
American College of Obstetricians and Gynecologists (2003, reaffirmed 2011). Neural tube defects. ACOG Practice Bulletin No. 44. Obstetrics and Gynecology, 102(1): 203-210. Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Other Works Consulted
Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier. Wapner RJ, et al. (2009). Prenatal diagnosis of congenital disorders. In RK Creasy et al., eds., Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 6th ed., pp. 221-274. Philadelphia: Saunders Elsevier.
ByHealthwise Staff Primary Medical Reviewer Sarah Marshall, MD - Family Medicine E. Gregory Thompson, MD - Internal Medicine Adam Husney, MD - Family Medicine Kathleen Romito, MD - Family Medicine Specialist Medical Reviewer Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Current as ofJune 6, 2017
Current as of:
June 6, 2017
Sarah Marshall, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Adam Husney, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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