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Rh Antibodies Screening: About This Test

What is it?

The Rh test is a blood test. It checks your blood for a marker called Rh. If you have Rh-negative blood and your baby has Rh-positive blood, your immune system may make antibodies that can harm your baby. When a pregnant woman has these antibodies, it is called Rh sensitization.

Why is this test done?

The Rh test is done in early pregnancy to find out if your baby is at risk for Rh disease. This can happen if you have Rh-negative blood and your baby has Rh-positive blood. If your Rh-negative blood mixes with Rh-positive blood, your immune system will make antibodies to attack the Rh-positive blood.

During pregnancy, these antibodies could attach to the baby's red blood cells. This can cause your baby to have serious health problems.

How can you prepare for the test?

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

What happens during the test?

A health professional takes a sample of your blood.

What else should you know about the test?

Rh sensitization does not cause any warning symptoms. A blood test is the only way to know if you are at risk for it.

  • If you are at risk:
    • Your doctor will give you one or more shots of Rh immune globulin (such as WinRho).
    • You will need to get another shot each time you get pregnant.
  • If you already have antibodies in your blood:
    • You will have regular tests to see how your baby is doing.
    • You may also see a doctor who specializes in high-risk pregnancies.

What happens after the test?

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

When should you call for help?

Watch closely for changes in your health, and be sure to contact your doctor, midwife, or nurse call line if you have any problems.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to

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