Alpha-Fetoprotein (AFP) Test

Why It Is Done

The AFP test is done to:

• Check the developing baby (fetus) of a pregnant woman for brain or spinal problems (called neural tube defects).
• Check the developing baby (fetus) of a pregnant woman for Down syndrome.
• Find certain cancers, especially cancer of the testicles, ovaries, or liver.
• Check how well treatment for cancer is working.

How To Prepare

You do not need to do anything before you have this test.

If you are pregnant, you will be weighed before the blood test, because the test results will be based on your weight. The test results are also based on race, age, and how many weeks you are in your pregnancy.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

In pregnant women, the amount of AFP gradually rises starting in the 14th week of pregnancy. It continues to rise until a month or two before the woman gives birth, and then it slowly decreases. Values are generally slightly higher for black women than they are for white women. Values are slightly lower for Asian women than they are for white women. An accurate estimate of the age of the baby is needed to understand the AFP value correctly.

The normal range of AFP values is adjusted for each woman's age, weight, and race; whether she has diabetes that needs injections of insulin; and the age of her baby (gestational age). If the age of the baby is changed after an ultrasound, the AFP must then be adjusted as well. Each woman and her doctor need to look at the range of AFP values that is normal for her when she has an AFP test.

A normal AFP result does not guarantee a normal pregnancy or healthy baby.

High values

• In a pregnant woman, high alpha-fetoprotein values can mean:
  • The age (gestational age) of the baby is wrong.
  • The woman is pregnant with more than one baby, such as twins or triplets.
  • The baby has a neural tube defect.
  • The baby's intestines or other abdominal organs are outside the body (called an abdominal wall defect or omphalocele). Surgery after birth will be needed to correct the problem.
  • The baby is not alive.
• In a nonpregnant adult, high alpha-fetoprotein values can mean:
  • Cancer of the liver, testicles, or ovaries is present.
  • Liver disease, such as cirrhosis or hepatitis, is present.
  • Alcohol use disorder is present.

Low values

In a pregnant woman, a low level of alpha-fetoprotein can mean:

• The age (gestational age) of the baby is wrong.
• The baby may have Down syndrome.

In a nonpregnant adult, alpha-fetoprotein is not normally present.

AFP test results can be abnormal, even when nothing is wrong with the baby.