Being Rh Negative
But for the Rh negative woman, this type of self-care may present a problem in her future. About 85% of the population in the United States has Rh positive blood, meaning that certain protein molecules are present on the surface of their blood cells. Your blood type (groups A, B, AB and O), as well as this "Rh factor," is determined genetically. As Rh positive blood is a dominant trait, the majority of Rh negative women carry children with Rh positive blood. During birth and, occasionally, at other times, some of the baby's blood may enter the mothers' circulation. In order to prevent your body from producing antibodies to combat baby's blood -- identified by the Rh positive factors and seen as foreign material -- an injection of Rh immune serum (such as RhoGam) should be given within 72 hours. Most Rh negative women routinely receive a dose of the serum as a prophylactic measure at 28 weeks of pregnancy, and then again shortly after delivery. The serum is also necessary after amniocentesis or if any hemorrhaging occurs at any time during pregnancy, or following a miscarriage or abortion. (Even at only a few weeks gestation, when the embryo is still tiny, the placenta may contain enough of the baby's blood to trigger the reaction.) With adequate prenatal care, Rh sensitization has become rare. Without treatment, your first baby typically will not be adversely affected, but future pregnancies will be at risk -- and the risk increases with each subsequent pregnancy. Prevention is the best cure, as the treatments available after sensitization are not always 100% effective. These may include the need for intrauterine blood transfusions, labor to be induced before term -- and, in severe cases, may result in birth defects, miscarriage or stillbirth. If you suspect you might be miscarrying, be sure to contact your caregiver immediately. In addition: If you don't know your blood type -- or your blood is Rhesus negative (Rh-) -- if you get pregnant, you should be aware of this. All of your future babies' health may depend on it.