Express Information Library (EIL)

Rh Incompatibility

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What is Rh incompatibility?

If you are a mother with Rh incompatibility, there is a substance in your baby's red blood cells that is not in your blood cells. This substance is usually called the Rho(D) factor. People who have the Rho(D) factor are Rh positive. People who do not have it are Rh negative. Being Rh negative or positive is something you inherit from your parents, just like you inherit the color of your eyes or hair.

While you are pregnant or delivering the baby, some of the baby's red blood cells may come in contact with your blood. Your body makes antibodies to the Rho(D) factor. This reaction is called sensitization. The antibodies may cross the placenta and destroy the red blood cells in your baby or any Rh-positive babies you have later. This destruction of red blood cells is called hemolytic disease. This disease can cause serious problems for the baby.

How does it occur?

Rh incompatibility happens only if you are Rh negative and your baby is Rh positive. It does not happen if you are Rh positive and your baby is Rh negative or if both of you are negative or positive.

Usually you are not exposed to a baby's blood until you give birth. This means that your first baby is not likely to be affected by the incompatibility. However, large amounts of the baby's blood often leak into the mother during delivery. Your body might then make antibodies. This can cause problems if you have another Rh-positive baby.

Sometimes the baby's blood may come in contact with your blood before delivery. This might happen, for example, during a miscarriage, termination of pregnancy (also called TOPs or abortions), or ectopic pregnancy; if the placenta breaks away from the uterus or is low in the uterus; or after amniocentesis or other similar tests.

If you are Rh negative and you got Rh-positive blood in a transfusion, you may have developed antibodies that will cause Rh incompatibility.

In most cases, development of antibodies can be prevented.

What are the symptoms?

You will have no symptoms. The baby will have symptoms if he or she develops hemolytic disease. The baby's red blood cells will start to break down, causing anemia. The anemia may cause yellow eyes and skin (jaundice), body swelling, and breathing problems, called hydrops or erythroblastosis fetalis. The baby might die in the womb if too much of the baby's blood is destroyed by the antibodies.

How is it diagnosed?

Blood tests are done to check for the Rho(D) factor to see if you are Rh positive or negative. Blood tests also check for antibodies against the Rho(D) factor. If you are Rh negative, the baby's father should also be tested. If the father's blood is Rh positive, the baby may inherit Rh-positive blood from him. If both you and the father are Rh negative, there will not be a problem because the baby will also be Rh negative.

Some of the tests used to check for hemolytic disease and its effects on the baby are:

How is it treated?

If you have already been sensitized by a previous birth, your baby may have hemolytic disease before birth. Your baby will be carefully checked with ultrasound scans and amniocentesis. These tests will help your provider know what treatment may be needed. For example, the baby may need a blood transfusion in the womb before birth. Sometimes early delivery by cesarean section (C-section) is necessary.

If you have not been sensitized, you will have a shot of Rho(D) immune globulin (RhoGAM) at about 28 weeks of pregnancy. If you have not delivered the baby within 12 weeks of this first shot, you will have a second shot. You may also be given a shot within 72 hours after a birth (if the baby is Rh positive), miscarriage, termination of pregnancy (also called TOPs or abortions), tubal (ectopic) pregnancy, or amniocentesis.

RhoGAM contains antibodies to the Rho(D) factor. The antibodies in the shot will destroy any red blood cells from the baby that are in your blood. Then your body will not make its own antibodies to the Rho(D) factor. If you have the shot at 28 weeks and after delivery, sensitization will be prevented and Rh incompatibility should not be a problem during your next pregnancy.

It is important to have the RhoGAM shot in all cases when the baby's blood could leak into your system. This includes:

If you have a threatened miscarriage but do not actually miscarry, you may also need a RhoGAM shot. Discuss this with your healthcare provider.

How long will the effects last?

Sensitization usually does not happen until after the birth of an Rh-positive baby. Therefore, in most cases Rh incompatibility is not a problem during your first pregnancy and delivery of an Rh-positive baby. However, later pregnancies and deliveries might be affected unless you are treated with RhoGAM.

Once you become sensitized, RhoGAM is not helpful. You will stay sensitized, and the effects are usually worse with each pregnancy.

What can be done to help prevent the problems of Rhincompatibility?

This problem of pregnancy has not happened often since the discovery of RhoGAM. RhoGAM can prevent sensitization. It is given to Rh-negative women right after every delivery, miscarriage, or termination of pregnancy (also called TOPs or abortions). It is also given to pregnant Rh-negative women after amniocentesis, after any bleeding episodes, and during the 7th month of pregnancy.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File SEXR5311.HTM Release 11.0/2008

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