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What Is Rh Incompatibility If you just found out you're pregnant, one of the first - and most important - tests you should expect is a blood-type test. This basic test determines your blood type and Rh factor. Your Rh factor may play a role in your baby's health, so it's important to know this information early in your pregnancy.
What Is the Rh Factor?People with different blood types have proteins specific to that blood type on the surfaces of their red blood cells. There are four blood types (A, B, AB, and O). Each of the four blood types is additionally classified according to the presence of another protein on the surface of red blood cells that indicates your Rh factor. If you carry this protein, you are Rh positive. If you don't carry the protein, you are Rh negative. Most people - about 85% - are Rh positive. But if a woman who is Rh negative and a man who is Rh positive conceive a baby, there is the potential for incompatibility. The baby growing inside the Rh-negative mother may have Rh-positive blood, inherited from the father. Statistically, at least 50% of the children born to an Rh-negative mother and Rh-positive father will be Rh positive. Rh incompatibility usually isn't a problem if it's the mother's first pregnancy because, unless there's some sort of abnormality, the fetus's blood does not normally enter the mother's circulatory system during the course of the pregnancy. However, during delivery, the mother's and baby's blood usually intermingles. When this happens, the mother's body will begin to produce antibodies (protein molecules in the immune system that recognize, and later work to destroy, any substance "foreign" to the body) against the Rh proteins that have been introduced into her blood. Rh antibodies are harmless until the mother's second or later pregnancies. If she is ever carrying another Rh-positive child, her Rh antibodies will now recognize the Rh proteins on the surface of the baby's blood cells as foreign. Maternal Rh antibodies will cross the placenta into the baby's bloodstream and attack those cells, causing swelling and rupture of the baby's red blood cells. A baby's blood count can get dangerously low when this condition, known as hemolytic or Rh disease of the newborn, occurs.
How Is Rh Disease of the Newborn Prevented and Treated?In generations past, Rh incompatibility used to be a very serious problem. Affected newborns were gravely ill or died from Rh disease. Fortunately, today there have been significant medical advances made in the prevention of complications resulting from Rh incompatibility, as well as in the treatment of any newborn affected by Rh disease. Today, when a woman with the potential to develop Rh incompatibility is pregnant, doctors administer a series of two Rh immune-globulin shots during her first pregnancy. The first shot is given around the 28th week of pregnancy and the second within 72 hours after giving birth. Rh immune-globulin acts like a vaccine, protecting against the development of the Rh antibodies that can cause complications during any future pregnancies. If a woman has a miscarriage, an amniocentesis, or any bleeding during pregnancy, a dose of Rh immune-globulin may also be given at that time. Again, an injection of Rh immune-globulin prevents the mother's body from producing any potentially dangerous Rh antibodies that can cause serious complications in the newborn later on. If a doctor determines that a woman has already developed Rh antibodies, then the pregnancy will be closely monitored to make sure that their levels are not too high. Rarely, if the incompatibility is severe and the baby is in danger, a series of special blood transfusions (called exchange transfusions) can be performed either while the baby is still in the uterus or after delivery. The purpose of exchange transfusions is to replace the baby's blood with red blood cells that have the Rh-negative factor. This procedure stabilizes the baby's level of red blood cells and minimizes further damage caused by circulating Rh antibodies already present in the baby's bloodstream. Because of the success rate of the Rh immune-globulin shots, exchange transfusions are needed in fewer than 1% of Rh-incompatible pregnancies in the United States today.
What Can Happen if Rh Disease Is Not Prevented?Although Rh incompatibility rarely causes complications in a first pregnancy and does not affect the health of the mother, if Rh antibodies develop, they can be potentially dangerous during subsequent pregnancies. Rh disease can result in severe anemia, jaundice, brain damage, and heart failure in a newborn. In extreme cases, it can cause the death of the fetus due to the depletion of too many red blood cells. If you're not sure what your Rh factor is and think you are pregnant, it's important to start regular prenatal care as soon as possible - including blood-type testing. With early detection and treatment of Rh incompatibility, you can focus on more important things - like welcoming a new, healthy baby into your household.
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