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Alpha-Fetoprotein (AFP) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Alpha-Fetoprotein (AFP) Test

The alpha-fetoprotein (AFP) test is a blood test performed during pregnancy to assess the risk of certain birth defects and genetic conditions in a developing baby.

Overview

An AFP test measures the level of alpha-fetoprotein in your blood. AFP is a protein primarily produced in the liver of a developing fetus. While some AFP naturally passes into the mother's blood, abnormal levels—either higher or lower than expected—may indicate an increased risk for specific health conditions. This test is typically conducted between 15 and 20 weeks of pregnancy.

For individuals who are not pregnant, this test may be used as an AFP tumor marker test to help diagnose certain cancers, particularly liver cancer.

Conditions Associated with Abnormal AFP Levels

Abnormal levels may suggest an increased risk for the following:

  • Neural tube defects: Serious conditions where the baby's brain, spine, or spinal cord do not form properly, such as spina bifida or anencephaly.
  • Down syndrome: A genetic disorder affecting physical and mental development.
  • Edwards syndrome (trisomy 18): An uncommon genetic condition often involving organ defects and abnormal head shape.
  • Abdominal or esophageal defects: Issues involving the baby's belly or the tube connecting the mouth to the stomach.

Why the Test is Performed

The test is routinely offered during the second trimester. Providers may specifically recommend it if you are at a higher risk due to:

  • A family history of birth defects.
  • Maternal age of 35 years or older.
  • A diagnosis of diabetes.
  • Use of certain medications or drugs during pregnancy that could harm the baby.

The AFP test is often part of a broader prenatal screening, such as a multiple marker test (triple screen) or a quad screen.

Understanding Results

It is important to note that this test cannot diagnose a condition; it only indicates risk levels. Results can be influenced by factors such as an incorrect due date, carrying multiple babies, or a false positive result.

  • Lower than normal levels: May indicate an increased risk for genetic disorders like Down syndrome or Edwards syndrome.
  • Higher than normal levels: May indicate an increased risk for neural tube defects or abdominal/esophageal defects.

If results are abnormal, your healthcare provider will typically order follow-up testing to investigate further.

Frequently Asked Questions

The AFP test measures only one protein, while the Quad Screen is a combination of four blood tests (AFP, hCG, estriol, and inhibin A) that assess the risk for neural tube defects and chromosomal abnormalities like Down syndrome. Providers may offer the Quad Screen as part of routine second-trimester screening because it provides a broader risk profile. If you have specific risk factors or if the initial AFP result is abnormal, your provider may recommend additional targeted testing rather than relying on a single marker.
Yes, in non-pregnant individuals, AFP is used as a tumor marker, primarily for hepatocellular carcinoma (liver cancer). It is often used in patients with chronic liver disease or cirrhosis to screen for cancer development. For patients already diagnosed with liver cancer, AFP levels are monitored over time to assess how well the tumor is responding to treatment; a decreasing level often indicates a positive response, while a rising level may suggest tumor growth or recurrence.
While the test itself is a simple blood draw, maternal diabetes is a risk factor that may influence the interpretation of AFP levels, as it can be associated with different patterns of fetal development. However, standard medications do not typically interfere with the laboratory measurement of AFP. It is important to inform your provider of all medications and medical conditions, such as diabetes, so they can interpret the results in the correct clinical context alongside other prenatal markers.
high AFP level during pregnancy is a screening result, not a definitive diagnosis. It indicates an increased risk for conditions such as neural tube defects (like spina bifida), abdominal wall defects, or multiple gestation (twins or triplets). If the level is elevated, your provider will likely recommend a detailed ultrasound to examine the baby's anatomy and possibly an amniocentesis to measure AFP levels in the amniotic fluid for a more accurate assessment.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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