Alpha-Fetoprotein (AFP) Test

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.

AFP is a protein mostly made in your developing baby's liver. Usually, some AFP passes from the baby into your blood. But certain medical conditions can make the baby's body release more or less AFP than usual.

When this happens, your AFP blood levels will be higher or lower than normal. Abnormal AFP levels may be a sign that your baby has an increased risk of a health problem, such as: A neural tube defect, a serious condition that happens when a baby's brain, spine and/or spinal cord do not form properly.; Down syndrome, a genetic disorder that changes the way a baby's body and brain develop. It can cause both mental and physical health challenges.

These problems may range from mild to severe.; Edwards syndrome (trisomy 18), an uncommon genetic condition that causes an abnormal head shape and many organ defects. Most babies with this condition die in the first year of life.; For people who aren't pregnant, an AFP blood test may be used to help diagnose certain cancers, especially liver cancer. When the test is used this way, it's called an AFP tumor marker test.

Why this test is done

An AFP test is routinely offered, usually between week 15 and 20 of your pregnancy. Your provider may especially recommend the test if your risk for having a baby with a birth defect or a genetic disorder is higher than usual because you:

• Have a family history of birth defects
• Are 35 years or older
• Have diabetes
• Have used certain medicines or drugs during pregnancy that could harm your baby

How to prepare

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

Sample type

Blood

Other names for this test

AFP Maternal; Maternal Serum AFP; msAFP screen