Alpha-Fetoprotein (AFP) Test
Reviewed
An AFP test is a blood test that measures the level of alpha-fetoprotein (AFP) in your blood when you are pregnant. The test checks your baby's risk of having certain birth defects and genetic problems, but it does not diagnose any health conditions. The test is usually done between 15 and 20 weeks of pregnancy.
Preparation and collection
No special preparation is needed.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- 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 results are abnormal, follow-up tests such as ultrasound or amniocentesis may be recommended.
Evidence source
U.S. National Library of Medicine: Alpha-Fetoprotein (AFP) Test