AFP Blood Test During Pregnancy

Unborn babies normally make alpha-fetoprotein (AFP), and it shows up in their mother's blood. Checking the level of AFP in a mom-to-be can show if her baby may have problems with their neural tube, what will become the brain and spinal cord.

AFP is one of the blood tests you have in a triple screen or quad screen. You can choose to get an AFP test or not. A genetic counselor can help you decide.

How It's Done

You do a maternal serum alpha-fetoprotein test when you're about 4 months pregnant.

A technician uses a needle to take a small sample of blood from a vein in your hand or arm. You may feel a small skin prick and have a little bruising or bleeding where the needle goes in. Then they'll send your blood to the lab.

What the Results Mean

A negative or normal test usually means your baby is healthy.

A positive test with a high AFP suggests a birth defect like spina bifida. That's typically a result of 2.5 times or more than the "average" level of AFP you'd expect to see at that point in your pregnancy.

A positive test with low AFP could mean a problem like Down syndrome or Edwards syndrome.

Don't worry if your test isn't normal. AFP only tells you there's a chance for a problem, not that there is one.

High AFP could mean you're further along than you thought, because your level keeps going up throughout your pregnancy. Your baby may make more AFP than normal, or you could be having twins (two babies make more AFP than one). Other things, including your race, weight, and having diabetes, can also affect your result.

What Happens Next

Sometimes you can get a false positive. That means the test says something's wrong when it's not. Your doctor will probably want to double-check your results. Another test often shows your baby is healthy.

When your AFP is too high or low, you can have more tests to find out why.

Your doctor will likely do an ultrasound to confirm how long you've been pregnant and how many babies there are. They'll also look closely for birth defects.

Continued

One of the next steps might be to see if there's AFP in the fluid around your baby with a test called amniocentesis. Your doctor uses a long, thin needle to go through your belly into the amniotic sac and take a small amount of fluid for the lab to check.

You may need to talk to a genetic counselor, who can help you understand your results and answer your questions.

If your baby might be born too early, your doctor will watch you closely.

If tests show your baby has a birth defect or other problem, you'll have to make difficult decisions. Talk to a specialist about what you can expect and what your options are so you can make the best choices for your family.

WebMD Medical Reference Reviewed by Neha Pathak, MD on November 03, 2017

Sources

SOURCES:

LabTestsOnline.org: "Second Trimester Maternal Serum Screening."

Maryland Department of Health: "AFP Testing for Improved Pregnancy Outcome."

Mayo Medical Labs: "Test ID: MAFP - Alpha-Fetoprotein (AFP), Single Marker Screen, Maternal, Serum."

American Pregnancy Association: "Maternal Serum Alpha-Fetoprotein Screening (MSAFP)."

Maryland Perinatal Associates: "Maternal Serum AFP Screening."

UpToDate: "Open neural tube defects: Risk factors, prenatal screening and diagnosis, and pregnancy management."

NHS Choices: "Amniocentesis."

© 2017 WebMD, LLC. All rights reserved.

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