Alpha-Fetoprotein (AFP) Test

An alpha-fetoprotein (AFP) test is a blood test you may have during pregnancy. Healthcare providers use it to screen for an increased risk of certain birth defects and genetic conditions.

The AFP test measures alpha-fetoprotein levels. Alpha-fetoprotein is a protein the fetus makes in its liver. A small amount passes into the pregnant woman’s blood, where it can be measured with a blood test. Irregular AFP levels can be a sign of a genetic disorder or birth defect.

What does the AFP test check for?

The test may detect:

• Genetic conditions, like Down syndrome
• Neural tube defects, like spina bifida or anencephaly
• Abdominal wall defects, like gastroschisis or omphalocele
• Incorrect due dates
• Twins or triplets

When is the test performed in pregnancy?

You typically have the AFP test between 16 and 22 weeks of pregnancy. The test is available to everyone, but it’s optional. It mostly depends on your pregnancy and the other prenatal screenings you’ve had. You can ask your provider if they recommend it for you.

Your provider may recommend an AFP test if you:

• Have a biological family history of birth defects or congenital conditions
• Are older than 35
• Have diabetes

How does an AFP test work?

An AFP test is a blood test. A healthcare provider inserts a small needle into a vein in your arm to collect a blood sample. The sample is sent to a lab where they see how much AFP it contains.

An AFP test usually takes less than five minutes. It’s quick and painless for most people. There’s no special preparation needed.

It may take several days to get your AFP test results. Your healthcare provider can review the results with you and let you know if you need additional testing.

What are the risks?

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 do the results of an alpha-fetoprotein test mean?

Your results will show whether your AFP level is low, within the expected range or high for your stage of pregnancy.

• Higher-than-usual AFP levels may mean the fetus has a higher risk of a neural tube defect, like spina bifida.
• Lower-than-usual AFP levels may mean the fetus has a higher risk of certain genetic conditions, like Down syndrome.

Higher or lower AFP levels don’t automatically mean the fetus has a genetic condition or a neural tube defect. The test is for screening only. It doesn’t diagnose conditions.

If your AFP levels are outside the normal range, your healthcare provider may recommend another blood test, an ultrasound or amniocentesis.

How accurate is the test?

An AFP test is a reliable screening tool. It can accurately detect about 8 in 10 cases of spina bifida and about 19 in 20 cases of anencephaly. Keep in mind that providers use AFP test results along with other test results — especially ultrasound — to make an official diagnosis.

When should I call my doctor?

Contact your pregnancy care provider if you have questions about your results or what they mean.

What is the AFP tumor marker test?

Most commonly, healthcare providers use AFP tests in pregnancy. But in some cases, your provider might order an AFP tumor marker test when you’re not pregnant.

Newborn babies typically have high AFP levels that drop to low ranges by age 1. Healthy adults have very low levels of AFP in their blood.

In an adult, high AFP levels may point to:

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

The AFP test is a tool to measure AFP levels. But an irregular test result doesn’t necessarily mean there’s a problem. Usually, your provider will order follow-up tests to learn more.

Can AFP tests detect all cancers?

No. AFP tests are only helpful for liver cancers and some ovarian or testicular cancers.

Can fatty liver cause high AFP levels?

Not usually. But AFP levels can be higher in people with certain liver diseases.