What is Rh Incompatibility

Rh incompatibility is a condition that occurs during pregnancy if a woman has Rh-negative blood and her baby has Rh-positive blood. “Rh-negative” and “Rh-positive” refer to whether or not the blood has a specific protein found on the surface of red blood cells (Rh factor).

If a woman has Rh factor, she is Rh-positive. If she does not have an Rh factor, she is Rh-negative. Having or not having an Rh factor does not affect the mother’s general health. However, it can cause problems during pregnancy.

What kind of problems can Rh incompatibility cause?

During pregnancy, blood from the baby can cross into the mother’s bloodstream, especially during delivery. If a mother is Rh-negative and the baby is Rh-positive, the mother’s defense (immune) system will react to the baby’s blood as if it were a foreign substance and will create certain proteins (antibodies) in response to it. This process is called sensitization. Once the mother is sensitized, her Rh antibodies will cross the placenta in future pregnancies and attack the baby’s Rh-positive blood as if it were a harmful substance.

Rh incompatibility can also happen if a pregnant woman who is Rh-negative receives a donation (transfusion) of Rh-positive blood.

How does this condition affect my baby?

The Rh antibodies that attack and destroy your baby’s red blood cells can lead to hemolytic disease in the baby. This is a condition in which red blood cells break down. This can cause:

• Yellowing of the skin and the whites of the eyes (jaundice).
• Fewer red blood cells in the body (anemia).
• Brain damage.
• Heart failure.
• Death.

These antibodies usually do not cause problems during a woman’s first pregnancy. This is because blood from the baby often crosses into the mother’s bloodstream during delivery, and the baby is born before many of the antibodies can develop. However, once antibodies have formed, they stay in a woman’s body. Because of this, Rh incompatibility is more likely to cause problems in second or later pregnancies (if the baby is Rh-positive).

How is this diagnosed?

When you become pregnant, you may have blood tests to determine your blood type and Rh factor. If you are Rh-negative, you may have another blood test called an antibody screen. The antibody screen shows whether you have Rh antibodies in your blood. If you do, it may mean that you have been exposed to Rh-positive blood before, and that you have a risk for Rh incompatibility.

To find out whether your baby is developing hemolytic anemia and how serious it is, health care providers may use more advanced tests, such as ultrasound.

How is Rh incompatibility treated?

This condition is treated with two shots (injections) of medicine called Rho (D) immune globulin. This medicine keeps your body from making antibodies that can cause serious problems for your baby or for future babies. You will get one shot around your seventh month of pregnancy and the other within 72 hours of your baby’s birth. If you are Rh-negative, you will need this medicine every time you have a baby with Rh-positive blood.

If you are Rh-negative and there is a high risk of blood transfer between you and your baby, you may be given Rho (D) immune globulin. The risk of blood transfer is high if you experience:

• Amniocentesis. This is a procedure to remove a small amount of the fluid that surrounds a baby in the uterus (amniotic fluid) so that it can be tested.
• A miscarriage or an abortion.
• An ectopic pregnancy. This is a pregnancy in which the fertilized egg attaches (implants) outside the uterus.
• Any vaginal bleeding during pregnancy.

If you already have antibodies in your blood, your pregnancy will be closely monitored. You will not be given Rho (D) immune globulin because it is not effective in these cases.

Summary

• Rh incompatibility is a condition that occurs during pregnancy if a woman has Rh-negative blood and her baby has Rh-positive blood.
• If a mother is Rh-negative and the baby is Rh-positive, the mother’s immune system will react to the baby’s blood as if it were a foreign substance, and will create antibodies.
• Rh antibodies that attack and destroy the baby’s red blood cells can lead to hemolytic disease in the baby.
• This condition is treated with a shot of medicine called Rho (D) immune globulin. This medicine keeps the woman’s body from making antibodies that can cause serious problems in the baby or future babies.