The Beginner's Guide to the Rh Factor in Pregnancy

When women are told they are "Rh incompatible" with their baby, it can lead to confusion and anxiety. However, there is little cause for concern with the modern advances in medicine. Rh incompatible can mean the potential for problems, but these problems can be easily prevented with proper medical care.

What is the Rh factor?

The Rh factor is one of the bodies many antigens, which is on an individual's blood cells. Everyone's blood cells either has the factor (they are Rh positive) or they don't (they are Rh negative). If a mother's blood cells lack the factor and her baby's don't, the mother's immune system will see the baby as a foreigner in her system, and her immune system will send out antibodies to attack the baby. This is what doctors are referring to when they use the words "Rh incompatibility."

How will the pregnant woman know if she is at risk, and what will be done if she is?

Pregnant women are tested for the Rh factor early in their pregnancies by their doctors. Most women are actually tested at their very first prenatal visit. If the woman is Rh positive, and most are, then there will be no cause for concern because the woman's immune system will not attack the baby whether it is Rh positive or negative.

When a woman is Rh negative, the baby's father will also be tested. If the baby's father is also Rh negative, the baby will be Rh negative as well, and there will no cause for concern. If the baby's father is Rh positive, however, there is a possibility that the baby will also be Rh positive, resulting in Rh incompatibility.

When is Rh incompatibility a problem?

Usually Rh incompatibility is not a problem in a first pregnancy unless the baby's blood mixes with the mother's at some point, either during delivery, miscarriage, or abortion. In that case, the mother's body would produce antibodies to attack the baby, but these antibodies would not do any harm until the mother becomes pregnant with another baby.

When the mother gets pregnant again, the antibodies could travel into the placenta and attack the fetal red blood cells, causing anemia in the baby.

What can be done to decrease the risk?

Most health care providers give a pregnant woman an injection of Rh-immune globulin, or Rhogam, at 28 weeks. Rhogam will prevent the woman's body from producing any antibodies. Another dose of Rhogam will be given to the mother 72 hours after delivery if the baby is found to be Rh positive.

If it is determined that a woman who is pregnant is at risk for Rh incompatibility, but she was not given Rhogam in her previous pregnancy, amniocentesis can be used to check the blood type of the baby. If the mother and baby are Rh incompatible, the mother's antibody levels will be monitored regularly, and if necessary, a transfusion of Rh-negative blood will be administered to the baby to prevent further complications.

Although many women have anxiety about the Rh factor in pregnancy, modern medicine has made it possible to detect and treat Rh incompatibility very effectively. In fact, less than 1 percent of pregnancies require a transfusion.

Sources:

www.mayoclinic.com

www.webmd.com