Key Points

• 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 your blood has Rh factor. Rh factor is a protein on red blood cells. If you have Rh factor, you're Rh-positive. If you don't have it, you're Rh-negative. Rh factor is inherited (passed from parents to children through the genes). Most people are Rh-positive.
• When you're pregnant-especially during delivery-blood from your baby can cross into your bloodstream. If you're Rh-negative and your baby is Rh-positive, your body will create antibodies (proteins) against the baby's Rh-positive blood.
• These antibodies usually don't cause problems during a first pregnancy. This is because the baby often is born before many of the antibodies develop. However, the antibodies stay in your body once they have formed. Thus, Rh incompatibility is more likely to cause problems in second or later pregnancies (if the baby is Rh-positive).
• The Rh antibodies can cross the placenta and attack the baby's red blood cells. This can lead to hemolytic anemia in the baby.
• Hemolytic anemia is a condition in which red blood cells are destroyed faster than the body can replace them. Without enough red blood cells, the body won't get enough oxygen. This can lead to serious problems or death in newborns.
• An Rh-negative woman who conceives a child with an Rh-positive man is at risk for Rh incompatibility. If you're Rh-negative and the father of your baby is Rh-positive, there's a 50 percent or more chance that the baby will have Rh-positive blood.
• If you're Rh-negative, your risk for Rh incompatibility also increases if you were exposed to Rh-positive blood before your current pregnancy. This could have happened during an earlier pregnancy, a miscarriage, an induced abortion, a blood transfusion, or certain tests (such as amniocentesis and chorionic villus sampling).
• Rh incompatibility is diagnosed with blood tests. To determine whether a baby is developing hemolytic anemia and how serious it is, doctors may use more advanced tests, such as ultrasound.
• Rh incompatibility is treated with a medicine called Rh immune globulin. If you're diagnosed with the condition during pregnancy, you'll receive Rh immune globulin in your seventh month of pregnancy and again within 72 hours of delivery.
• Treatment for a baby who has hemolytic anemia will vary depending on how severe the condition is.
• Rh incompatibility can be prevented with Rh immune globulin, as long as the medicine is given at the correct times. Once you have formed Rh antibodies, the medicine will no longer help.
• With prompt and proper prenatal care and screening, you can prevent the problems of Rh incompatibility. Once your doctor is aware of your risk, he or she can carefully monitor your pregnancy and promptly treat any problems that arise.