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Rh Factor Disease

A blood-type test is performed when woman finds out that she is pregnant to determine her blood type and Rh factor. This information is important to monitor the health of the baby.

The red blood cells (RBCs) have proteins on the surface that are used to classify them into four blood types,  A, B, AB, and O blood type.

Each of these four blood types is also classified according to the presence of another protein that indicates the Rh factor. If the blood cells have this protein, the blood is Rh positive (Rh+). If the blood cells do not have this protein, the blood is Rh negative (Rh-). About 85% of people are are Rh positive

The baby with Rh-positive blood may develop problems if conceived by a mother with Rh-negative blood. This can occur if the father of the baby has Rh positive blood and passes that trait onto the child. This mismatch of Rh factors is called Rh incompatibility.

Rh incompatibility is not usually a problem during a mother's first pregnancy because 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 can intermingle. If this happens, the mother's body recognizes the Rh protein as a foreign substance and can begin producing antibodies against the Rh proteins introduced into her blood.

A pregnant woman with Rh-negative blood can also be exposed to Rh-positive blood during blood transfusions with Rh-positive blood, or following miscarriage or ectopic pregnancy.

Rh antibodies are harmless until the mother's second or later pregnancies. If she has another Rh-positive baby, her Rh antibodies will recognize the Rh proteins on the surface of the baby's blood cells as foreign substances and attack those cells. This can lead to destruction of the baby's red blood cells. This condition, known as hemolytic anemia or Rh disease of the newborn, can lead to dangerously low levels of red blood cells and severe anemia in the baby

Preventing and Treating Rh Disease of the Newborn

Significant medical advances have been made to help prevent complications from Rh incompatibility and to treat any newborn affected by Rh disease.

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, preventing the mother's body from producing any potentially dangerous Rh antibodies that can cause serious complications in the newborn or complicate any future pregnancies.

A dose of Rh immune-globulin may also be given if a woman has a miscarriage, an amniocentesis, or any bleeding during pregnancy.

If a doctor determines that a woman has already developed Rh antibodies, then the pregnancy will be closely monitored to make sure that those levels are not too high. In rare cases, 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.

Exchange transfusions replace the baby's blood with RBCs that are Rh-negative. 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.

The success rate of the Rh immune-globulin shots is very high so exchange transfusions are required in fewer than 1% of Rh-incompatible pregnancies today.

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