Alpha-Fetoprotein (AFP) Test

What is an alpha-fetoprotein test?

The alpha-fetoprotein (AFP) test is a blood test for pregnant people. Healthcare providers use the AFP test to check a fetus’s risks of birth defects or genetic conditions.

The AFP test measures alpha-fetoprotein levels. Alpha-fetoprotein is a protein that develops in the liver of a fetus. Irregular AFP levels in pregnant people can be a sign of a genetic disorder or birth defect (congenital disability).

What is the AFP tumor marker test?

Most commonly, healthcare providers use AFP tests in a pregnant person. But in some cases, your healthcare provider might order an AFP tumor marker test when you’re not pregnant. The tumor marker test has different purposes than the AFP test for pregnant people.

Newborn babies typically have high AFP levels that drop to low ranges by age 1. In an adult, high AFP may point to:

• Cirrhosis.
• Hepatitis A, hepatitis B or hepatitis C.
• Liver cancer.
• Ovarian or testicular cancer.
• Toxic hepatitis or autoimmune hepatitis.

Healthcare providers may also use AFP tumor marker tests to plan cancer treatment. For example, if you have high AFP levels and liver cancer, targeting cancer cells with specific drugs (targeted therapy) may be an effective treatment.

It’s important to understand that AFP tumor marker tests are simply tools to measure AFP levels. They can help diagnose cancer or other conditions. But an irregular test result doesn’t necessarily mean there’s a problem. Usually, your provider will order follow-up tests to learn more.

When is the AFP test performed in pregnancy?

Pregnant people typically have the AFP test between 16 and 22 weeks of pregnancy.

All pregnant people should get the AFP test, but your healthcare provider may especially recommend it if you:

• Are older than 35.
• Have a family history of birth defects.
• Have diabetes.

What does the AFP test check for?

The test may detect:

• Genetic disorders, such as Down syndrome or Turner syndrome.
• Incorrect due dates.
• Multiples, such as twins or triplets.
• Neural tube defects, such as spina bifida or anencephaly.

How does an AFP test work?

An AFP test is a blood test. During blood tests, your healthcare provider:

1. Places a small needle into one of your arm veins.
2. Collects a tube (vial) of blood.
3. Removes the needle and applies cotton and a bandage to the area.

AFP tests usually take less than five minutes. They're quick and painless for most people.

If you have a fear of needles (trypanophobia) or anxiety about getting blood draws, tell the healthcare provider who’s taking your blood. It may help to practice breathing exercises, look away from the needle or bring a friend for support.

How do I prepare for an AFP test?

There’s no special preparation for an AFP blood test. Generally, staying hydrated by drinking plenty of water can help the blood draw go more quickly and smoothly. Hydration prevents your veins from tightening (constricting) and decreases the chance of blood pressure changes.

What are the risks of an AFP test?

All blood tests may cause some soreness, bruising or redness near where the needle was inserted. Usually, these symptoms are mild and go away within a day.

What should I know about the results of an alpha-fetoprotein test?

If your AFP test results are abnormal, your provider will order more tests to confirm the diagnosis. Higher than usual AFP levels can point to neural tube defects. Lower than usual AFP levels may indicate that the fetus has a genetic disorder such as Down syndrome.

It’s important to understand that irregular AFP levels don’t automatically mean the fetus has a genetic condition or a neural tube defect. Irregular AFP levels can also mean:

• You are having multiples, such as twins.
• Your due date was miscalculated.

Is an AFP test the only test I need?

If your AFP levels are outside the normal range, your provider will likely order more tests to diagnose or rule out conditions.

During pregnancy, you'll have other prenatal tests that check for genetic disorders along with the AFP test. For example, you usually have a triple screen test around the same time as an AFP test. The triple screen looks at your levels of specific hormones. Triple screen tests also check for genetic disorders such as Down syndrome.

If your test results show that the fetus may have a genetic condition, your provider may recommend chorionic villus sampling (CVS). CVS is a genetic test that evaluates cells from the placenta. It can detect genetic disorders such as:

• Cystic fibrosis.
• Down syndrome.
• Sickle cell disease.
• Tay-Sachs disease.

What else should I ask my doctor?

You may also want to ask your healthcare provider:

• When should I schedule an AFP test?
• What do my AFP levels mean?
• What other tests do I need to check for genetic disorders?
• What other tests do I need to check for neural tube defects?

How accurate is the AFP test?

AFP tests are good tools for detecting genetic disorders or neural tube defects. Up to 9 in 10 fetuses with neural tube defects were diagnosed because the AFP test detected abnormalities. But AFP tests aren’t perfect.

In every 1,000 pregnant people who get the AFP test, up to 50 get abnormal results. Of those 50, only about 1 in 16 have a baby with a genetic condition or neural tube defect.

A note from Cleveland Clinic

Alpha-fetoprotein tests are blood tests to check AFP between 16 and 22 weeks of pregnancy. Irregular AFP levels may point to the presence of a genetic disorder or neural tube defect in the fetus. It’s important to understand that AFP tests are screening tools, not diagnostic ones. Atypical AFP levels don’t automatically mean the fetus has a disorder. If you have irregular AFP test results, your provider will likely order more tests to diagnose or rule out genetic conditions or neural tube defects.