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Rh Sensitization During Pregnancy - Exams and Tests

If you are pregnant, you will have your first prenatal tests during your first trimester. Every woman has her blood tested at the first prenatal visit to see what her blood type is. If your blood is Rh-negative, it will also be tested for antibodies to Rh-positive blood. If you have antibodies, that means that you have been sensitized to Rh-positive blood. The antibodies can now kill Rh-positive red blood cells.

If you are Rh-negative and your partner is Rh-positive, your fetus is likely to be Rh-positive.

If you are pregnant or have miscarried, or if you have had an elective abortion, a partial molar pregnancy, or an ectopic pregnancy, you will need testing to see if you have been sensitized to Rh-positive blood.

If you are Rh-negative

All pregnant women have an indirect Coombs' test during early pregnancy.

  • At the first prenatal visit, your blood is tested to see if you have been previously sensitized to Rh-positive blood. If you are Rh-negative and test results show that you are not sensitized, a repeat test may be done between 24 and 28 weeks.
  • If test results at 28 weeks show that you have not been sensitized, no additional tests for Rh-related problems are done until delivery (barring complications such as placenta abruptio). You will also have a shot of Rh immune globulin. This lowers your chances of being sensitized during the last weeks of your pregnancy.
  • If your newborn is found to be Rh-positive, your blood will be screened again at delivery with an indirect Coombs' test to see if you have been sensitized during late pregnancy or childbirth. If you have not been sensitized, you will have another shot of Rh immune globulin.
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