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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 do you prepare for the test?

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How is the test done?

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

What happens after the test?

  • You will probably be able to go home right away. It depends on the reason for the test.
  • You can go back to your usual activities right away.

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?

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