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AFP Tests

Outline of woman showing blood vessels and baby in uterus. Blood vessels connect to uterus. Arrow shows blood going into test tube. Symbols from baby move into blood stream and out into test tube.
When you're pregnant, substances from the fetus mix with your blood. Your doctor can find those substances in a blood sample taken from your arm.

An AFP (alpha-fetoprotein) test is a simple blood test. It can show whether your fetus has signs of some birth defects. This test is done between weeks 15 and 20 of pregnancy.

Your AFP Test Results

You’ll get your AFP test results within 2 weeks. These results show the presence of certain fetal substances in your blood. Your results can alert your doctor to possible birth defects.

Most AFP results are negative (normal). This means the test results show no signs of the birth defects tested for. Sometimes results are positive (abnormal). Often, this is simply because:

  • Your due date is different than first thought.

  • You have twins.

Some positive results show that the fetus may have one of the following birth defects:

  • Neural tube defects (problems with the spine, such as spina bifida)

  • Abdominal wall defects (problems with the body of the fetus)

  • Genetic defects (physical or mental problems, such as Down syndrome)

While it happens rarely, AFP test results can be wrong. These are called false negatives or false positives. Be sure to ask your healthcare provider any questions you have about your results.

Understanding AFP Tests

An AFP test is only a screening test. The most it can do is point to a possible problem. If your results point to a problem, other tests will be needed to confirm the results. Keep in mind that most AFP test results are normal. Even when they’re not, the results of the follow-up tests most often are.

Online Resources

American Pregnancy Association  http://www.americanpregnancy.org/prenataltesting/afp.html

© 2000-2011 Krames StayWell, 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.