If you’re pregnant, you should know about this test – RH incompatibility

What is RH typing?

You’ve probably heard of different types of blood, like A, B, O, plus and minus and maybe some others. The letters A B and O are referring to different types of antigens, A, B, or neither of them (O). When your body produces white blood cells (an important part of your immune system), they are chosen according to which ones know not to attack your own cells. If for example your blood cells have an A antigen but no B antigen, then your immune system knows that if they come across an A antigen than it’s okay, but if they come across a B antigen it’s something foreign to the body and they need to get rid of it. Aside from ABO antigens, there is another group of antigens called RH antigens. This what the plus and minus comes from when determining blood type. AB+ means that you have A antigens, B antigens, as well as RH antigens. In fact there are many other groups of antigens, but this post will focus on RH. RH typing is simply your blood type according to the RH antigens.

Why is it relevant to pregnant women?

The same rules apply for RH antigens that do for ABO antigens with respect to the immune system. But what happens for example if a nice couple create a baby, and that baby develops a blood type that is different from the blood type of it’s mother? During the first pregnancy, this might not be a problem because there is a barrier between the fetus and the mother. However during birth, the mother might be exposed to the fetus’ blood, and antibodies that the blood of the fetus contains might start up the engines of the mother’s immune system, creating antibodies against this type of blood. That couple’s next child receives the antibodies from it’s mother, and this can create a dangerous problem for that fetus.

Who should be tested?

The recommendation is for all women to be tested during their first prenatal visit to the doctor.

What can be done about it?

There are certain treatment options after birth for effected babies. This can include phototherapy, blood transfusions, or other fluids that may be given to the baby IV. However if you are able to diagnose RH incompatibility during pregnancy than there are also treatment options that can prevent the complications. This could include injecting immune globulins, or other transfusional treatments ins severe cases.

*Please comment to us if you found this information useful, or if you have any questions about the topic.

Knowledge is power. It’s very important for each of us to understand what our options are, and what evidence supports each option. Preventing diseases before they start is often the most efficient way to be healthy, and this starts by screening for the diseases that are appropriate for us depending on age, gender, and other factors. Download our app to go through a short list of questions, and receive a personalized list of the appropriate screening recommendations for you. More information about each of these tests is provided through the app, so that you can stay informed and educated.


Here are a few studies which give insight into the efficacy of screening and early treatment for RH incompatibility. Feel free to contact us for more information about the matter, we would be happy to provide more information.

U.S. Preventive Services Task Force. Guide to Clinical Preventive Services, 2nd ed. Washington, DC: Office of Disease Prevention and Health Promotion, 1996.

Harris RP, Helfand M, Woolf SH, Lohr KN, Mulrow CD, Teutsch SM, Atkins D, for the Methods Word Group, third U.S. Preventive Services Task Force. Current methods of the U.S. Preventive Services Task Force: a review of the process. Am J Prev Med2001;20(3S):21-35.

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