Skip to content
    Font Size

    Prenatal Antibody Testing

    By Linda Rath
    WebMD Medical Reference
    Reviewed by Neha Pathak, MD

    When you're a mom-to-be, one of the prenatal tests you may get is an antibody test or antibody screening. It looks for certain antibodies, special proteins made by your immune system, in your blood.

    You might have these antibodies if you've gotten blood from a donor or given birth before. There's also a chance your body could make them when your and your baby's blood types don't match.

    Some of these antibodies can be passed from you into your baby's bloodstream, where they could do harm. Antibody testing lets you and your doctor know if you have them so you can take steps to protect your growing baby.

    Why You Get Tested

    Your immune system makes antibodies to fight things it sees as "not you." Most of the time, that's great because antibodies usually target germs. And when you're pregnant, your immune system takes care of your baby, too. But if your red blood cells are different from your baby's, that may cause problems.

    By far, the most common one is related to the + or - part of your blood type, called the Rh factor. Many people are Rh-positive, which means they have the Rh protein on their red blood cells. Rh-negative people don't. So they'll make antibodies to attack any Rh-positive blood cells that get into their body.

    If you're Rh-negative and your baby is Rh-positive, your blood might have Rh antibodies that could spread to your baby's blood, where they'd attack and destroy your baby's red blood cells. This can cause a type of anemia that's very serious and could be fatal.

    Your body might have made other antibodies that could attack your baby's red blood cells, too.

    How It's Done

    You should get your blood type checked early in your pregnancy, perhaps at your first prenatal visit. If you're Rh-negative, then you should have the antibody test during the first 3 months that you're pregnant. (If you're Rh-positive, your doctor may still want to do an antibody test in your first trimester.)

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

    Then they'll send the sample to a lab to run an indirect Coombs test, which checks for red blood cell antibodies.

    Hot Topics

    WebMD Video: Now Playing

    Click here to wach video: Dirty Truth About Hand Washing

    Which sex is the worst about washing up? Why is it so important? We’ve got the dirty truth on how and when to wash your hands.

    Click here to watch video: Dirty Truth About Hand Washing

    Popular Slideshows & Tools on WebMD

    disciplining a boy
    Types, symptoms, causes.
    fruit drinks
    Eat these to think better.
    bald woman smelling flowers
    Complementary therapies to ease symptoms.
    embarrassed woman
    Do you feel guilty after eating?
    diabetes highlighted
    4 early warning signs.
    birth control pills
    Which kind is right for you?
    Remember your finger
    Are you getting more forgetful?
    sticky notes on face
    10 tips to clear your brain fog.
    Close up of eye
    12 reasons you're distracted.
    Trainer demonstrating exercise for RA
    Exercises for your joints.
    Senior woman using diabetes test kit
    Each one takes 10 minutes or less.
    woman having a good day
    Revitalize your life.

    Pollen counts, treatment tips, and more.

    It's nothing to sneeze at.

    Loading ...

    Sending your email...

    This feature is temporarily unavailable. Please try again later.


    Now check your email account on your mobile phone to download your new app.