What is Alpha-Fetoprotein Test?
Alpha-fetoprotein (AFP) is a protein produced in the liver of a developing fetus. During a baby’s development, some AFP passes through the placenta and into the mother’s blood. An AFP test measures the level of AFP in pregnant women during the second trimester of pregnancy. Too much or too little AFP in a mother’s blood may be sign of a birth defect or other condition. These include:
- A neural tube defect, a serious condition that causes abnormal development of a developing baby’s brain and/or spine
- Down syndrome, a genetic disorder that causes intellectual disabilities and developmental delays
- Twins or multiple births, because more than one baby is producing AFP
- Miscalculation of due date, because AFP levels change during pregnancy
An AFP blood test is used to check a developing fetus for risk of birth defects, such as neural tube defects or Down syndrome.
Why is Alpha-Fetoprotein Test performed?
An AFP test is a routine screening test that’s given to expectant mothers between the 14th and 22nd weeks of their pregnancy. It is most accurate between the 16th and 18th weeks, so it’s important to know exactly when you became pregnant.
AFP testing is usually part of a quad screen. This screening exam also tests your levels of:
- Human chorionic gonadotropin (HCG)
- Estriol, which is a hormone produced by your placenta and your baby’s liver
- Inhibin A, which is a hormone produced by your placenta
Doctors will use your quad screen results, your age, and your ethnicity to help determine the chances that your unborn baby has a genetic birth defect. Defects detected by this type of screening can include neural tube defects, such as spina bifida, and chromosomal abnormalities, such as Down syndrome. The AFP results will help your doctor determine if you need further tests for these conditions. A positive test doesn’t necessarily mean your unborn baby will have a birth defect.
The AFP test is especially important for women who are at high risk of having children with birth defects, including women:
- Who are 35 or older
- With a family history of birth defects
- Who used harmful medications or drugs during their pregnancies
- Who have diabetes
If you aren’t pregnant, an AFP test can help to diagnose and monitor certain liver conditions, such as liver cancer, cirrhosis, and hepatitis. It can also help detect several other cancers, including cancers of the:
What should I know before receiving Alpha-Fetoprotein Test?
There are very few risks associated with having your blood drawn for an AFP test. You may feel slightly faint or have some soreness or pain at the puncture site. There’s a small chance of excessive bleeding or hematoma, which occurs when blood accumulates under your skin. There is also a very slight risk of infection at the puncture site.
How to prepare for Alpha-Fetoprotein Test?
You don’t need any special preparation for an AFP test.
What happens during Alpha-Fetoprotein Test?
You’ll need to get your blood drawn for an AFP test. Having blood drawn is an outpatient procedure that’s usually performed at a diagnostic lab. The procedure takes only a few minutes and is relatively painless. No special preparation is necessary before an AFP test.
A healthcare professional will use a small needle to withdraw blood from a vein, usually in your arm or hand. A laboratory specialist will analyze the sample. Results are typically available within one to two weeks.
What happens after Alpha-Fetoprotein Test?
This test doesn’t require any special aftercare. You may resume your daily activities unless instructed otherwise by your doctor.
If you have any questions about the Alpha-Fetoprotein Test, please consult with your doctor to better understand your instructions.
Explanation of results
What do my results mean?
For women who aren’t pregnant as well as men, the normal amount of AFP is usually less than 10 nanograms per milliliter of blood. If your AFP level is unusually high but you aren’t pregnant, it may indicate the presence of certain cancers or liver diseases.
If you’re pregnant you have higher-than-normal AFP levels, it can indicate a neural tube defect in your developing baby. However, the most common cause of elevated AFP levels is inaccurate dating of the pregnancy. AFP levels vary widely during pregnancy. The test will be inaccurate if you’ve been pregnant for a longer or shorter period of time than you thought.
If you’re pregnant and your AFP level is unusually low, it could indicate that your fetus has a chromosomal abnormality, such as Down syndrome or Edwards syndrome.
You can have an abnormal AFP reading due to a multiple pregnancy, such as having twins or triplets. An abnormal AFP reading can also be due to fetal death.
According to the American Pregnancy Association, results are abnormal for 25 to 50 pregnant women out of every 1,000 pregnant women given an AFP test. However, only between 1 in 16 and 1 in 33 women who have abnormal results will actually have a baby with a birth defect.
If you have abnormal test results, it doesn’t necessarily mean that your child will have a birth defect. It only indicates that more tests are necessary for your doctor to make a diagnosis. Your doctor may perform another AFP test followed by an ultrasound to record images of your unborn child.
Your doctor may order a more invasive test, such as an amniocentesis, if your results are still abnormal. In amniocentesis, your doctor uses a needle to withdraw a small amount of amniotic fluid from around the fetus for analysis.
Depending on the laboratory and hospital, the normal range for Alpha-Fetoprotein Test may vary. Please discuss with your doctor any questions you may have about your test results.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: November 6, 2018 | Last Modified: November 6, 2018
Alpha-Fetoprotein Test. https://www.healthline.com/health/alpha-fetoprotein. Accessed October 25, 2018.
Alpha-Fetoprotein (AFP) Test. https://medlineplus.gov/lab-tests/alpha-fetoprotein-afp-test/. Accessed October 25, 2018.