Rh factor, or Rh antigen, is a substance present by heredity in the blood of most people. Only 15 percent of us lack Rh factor, or have Rh-negative blood. Years ago, babies often died from what was known as Rh incompatibility, or rhesus disease. Today, we can prevent this from happening. If both you and your husband have Rh-negative blood, then the baby will also have this blood type, and no treatment is needed. If, however, your blood is Rh-negative and your husband’s is Rh-positive, the baby may have Rh-positive blood. In this case, your body could begin producing antibodies to your baby’s red blood cells. If you have never been pregnant before, your baby would be unaffected by these antibodies. They would remain dormant and harmless unless you became pregnant again. Then, if your baby were Rh-positive, the antibodies could cross the placenta and attack the baby’s red blood cells. This could cause anemia and mild to severe jaundice in the baby. To prevent this problem, an Rh-negative mother with an Rh-positive partner receives a shot of Rh immune globulin, or RhoGAM, at 28 weeks of pregnancy and again within 72 hours of giving birth. Rh immune globulin is also given to an Rh-negative woman after a miscarriage, an ectopic pregnancy, or an induced abortion, and at the time of amniocentesis, CVS, or another invasive procedure during pregnancy. A shot of RhoGAM should be considered, too, if an Rh-negative woman experiences any significant bleeding or blunt trauma, such as from a car accident or fall, while she is pregnant. This kind of injury can also cause Rh sensitization.
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