Alpha-Fetoprotein (AFP) Test

Why this test may be ordered

• Fulfill a routine offering during pregnancy (usually between 15 and 20 weeks).
• Especially recommended if you have a family history of birth defects, are 35 years or older, have diabetes, or have used certain medicines or drugs during pregnancy that could harm your baby.

Preparation and collection

You don't need any special preparation for an AFP test.

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

There is very little risk to you or your baby with an AFP blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

The results of your AFP test tell you whether your baby is more or less likely to have certain birth defects and genetic disorders. The test can't diagnose any conditions.

• Normal AFP level: Normal AFP test results mean that it's unlikely that your baby has a problem. Limitation: But it's possible for a test result to be normal and miss a problem that does exist. Next step: If you have questions about your results, talk with your provider.
• Lower than normal AFP level: Lower than normal AFP levels may mean your baby has an increased risk of a genetic disorder such as Down syndrome or Edwards syndrome. Limitation: Abnormal AFP results don't always mean that your baby has an increased risk of a serious problem. If your due date is wrong, your AFP blood level may seem abnormal when it's just right for how far along you really are in your pregnancy. Next step: If your AFP test results aren't normal, you will likely have more tests to help find out why.
• Higher than normal AFP level: Higher than normal AFP levels may mean your baby has an increased risk of: A neural tube defect, such as: Spina bifida, a condition in which the bones of the baby's spine don't close around part of the spinal cord. It often causes damage to the spinal cord and nerves. Anencephaly, a condition in which most of the baby's brain and skull don't develop. Almost all babies with this condition die shortly after birth. A defect in the abdomen (belly) or esophagus (the tube that carries food from the baby's mouth to the stomach). Limitation: Being pregnant with more than one baby. Each baby makes AFP, so your AFP blood levels will be higher with two or more babies. A false positive result. This means that your AFP results show an increased risk of a problem when there's really nothing wrong with your baby. Next step: If your AFP test results aren't normal, you will likely have more tests to help find out why.

• The AFP test is a screening test and does not diagnose any health conditions.
• A normal result does not rule out the possibility of a birth defect or genetic disorder (false negative possible).
• An abnormal result may be a false positive and does not confirm a problem.
• AFP levels vary with gestational age; an incorrect due date can lead to abnormal results.
• Abnormal results may cause emotional distress and require additional testing.

What to do next

If your AFP test results aren't normal, you will likely have more tests to help find out why. If you have questions about your results, talk with your provider.

• What is an alpha-fetoprotein (AFP) test?
• Why do I need an AFP test?
• What happens during an AFP test?
• Will I need to do anything to prepare for the test?
• Are there any risks to the test? What do the results mean?

Evidence source

Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.

U.S. National Library of Medicine: Alpha-Fetoprotein (AFP) Test

More lab tests A–Z

• Allergy Blood Test
• Allergy Skin Test
• Alpha-1 Antitrypsin Testing
• Alpha-fetoprotein (AFP) tumor marker test
• ALT Blood Test
• Ammonia Levels