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, non-pregnant 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.
In men, non-pregnant women, and children, AFP in the blood can mean 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 tumours, and renal cell cancer.
Health Tools help you make wise health decisions or take action to improve your health.
|Decision Points focus on key medical care decisions that are important to many health problems.|
|Pregnancy: Should I Have the Maternal Serum Triple or Quadruple Test?|
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 pregnancy.
The health professional drawing blood will:
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 pinch.
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.
Normal AFP values may vary from lab to lab. 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. An ultrasound may be done to check the baby's age more accurately.
|Men and non-pregnant women:|
|Women 15–18 weeks pregnant:|| |
10-150 ng/mL or mcg/L
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 correctly.
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.
In a pregnant woman, a low level of alpha-fetoprotein can mean:
In a non-pregnant adult, alpha-fetoprotein is not normally present.
Things that may affect the results of your test include:
- American College of Obstetricians and Gynecologists (2003, reaffirmed 2008). Neural tube defects. ACOG Practice Bulletin No. 44. Obstetrics and Gynecology, 102(1): 203–210.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- 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.
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Primary Medical Reviewer||Adam Husney, MD, MD - Family Medicine|
|Primary Medical Reviewer||Brian D. O'Brien, MD - Internal Medicine|
|Specialist Medical Reviewer||Kirtly Jones, MD, MD - Obstetrics and Gynecology|
|Last Revised||July 27, 2010|
Last Revised: April 27, 2012
This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.