Rh Disease (Hemolytic Disease of the Newborn)

When foreign cells enter the body, an immune response is triggered, and the body produces antibodies targeted specifically against proteins on the foreign cells. Such a response can occur during pregnancy if a baby's fetal red blood cells carry a protein called Rh factor but the mother's cells do not. The result can be widespread destruction of the baby's red blood cells, a condition known as Rh disease or hemolytic disease of the newborn. Fortunately, steps can be taken to prevent this complication. Treatment is also available for the 5,000 cases that still occur in the United States each year.

HOW DOES RH DISEASE DEVELOP?
The presence or absence of Rh factor is designated by the + or - after your blood type. People who have A+, B+, AB+ or O+ blood have the Rh factor; those who have A-, B-, AB- or O- blood do not.

Rh disease occurs when a mother, father and child have incompatible Rh blood types (meaning they have the Rh protein) and the mother has Rh- blood (meaning she does not have the protein). When Rh+ fetal blood cells leak into an Rh- mother's bloodstream, the mother's immune system begins to manufacture antibodies that will recognize and destroy Rh+ cells.

Because it takes time to mount an antibody defense, the first Rh incompatible child is unaffected. If the fetus in a subsequent prenancy is also Rh+, however, the mother's immune systems will recognize the fetal blood as foreign and launch an antibody attack against it, causing Rh disease in the baby.

m Newborns with Rh disease become severely jaundiced because of the buildup of bilirubin (the breakdown product of dead red blood cells). They also have swelling of the liver and spleen as a result of stepped-up production of new red blood cells. If the fetus or newborn does not receive a transfusion of Rh- blood, the heart and blood vessels collapse and generalized swelling sets in. Rh disease that progresses this far is called bydrops fetalis.

WHEN SHOULD I SUSPECT THE POSSIBLITY OF RH INCOMPATIBILITY?
Couples should make a point of knowing each other's blood types. If the woman is Rh- and the man is Rh+, they should tell the obstetrician and pediatrician early in the pregnancy.

WHAT TREATMENTS ARE AVAILABLE?
Obstetricians routinely determine blood type in pregnant women. If there is a possibility of Rh incompatibility with the baby, the woman is given an injection of a preparation called RhoGam during pregnancy and immediately after birth. RhoGam suppresses the antibody response in subsequent pregnancies.

Severe Rh incompatibility disease is now rare for several reasons, foremost of which is the availability of good prenatal and obstetrical care. In addition, only 15 percent of the population is Rh-, so the chances of Rh incompatibility are actually fairly low. Also, fetal blood enters the maternal bloodstream in only about 50 percent of pregnancies, so even if the fetus and mother are incompatible, an antibody reaction may not occur. Further, only ten percent of women manufacture enough antibodies to harm the fetus.

In the rare cases in which severe Rh disease does develop, the baby is given an immediate exchange transfusion of Rh- blood. This procedure removes accumulated bilirubin and provides the baby with red cells that will not be destroyed by the mother's antibody.

Excerpt from THE DISNEY ENCYCLOPEDIA OF BABY & CHILD CARE, © 1995 DSH Communications, Inc. This material is based on current medical research and, to the best of the editors' knowledge and understanding, is accurate and valid. However the reader should not use information contained in this material to alter a medically prescribed regimen or as a form of self-treatment, without seeking the advice of a licensed physician.