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Sanford Pincus, age 17, of North Brunswick, N.J., for his question:

WHAT IS THE Rh FACTOR?

In 1940, two scientists named Karl Landsteiner and Alexander Wiener discovered a substance in the red blood cells of most persons. Experimenting with rhesus monkeys, they named the substance Rh factor for the animals. Earlier, Landsteiner had won the Nobel Prize for his 1930 discovery of the main types of human blood.    His discovery made safe blood transfusions possible for the first time.

About 85 percent of the population has the element    known as Rh factor in its blood. It is an inherited ingredient.

If the factor is present in a person's blood, he is said to be Rh positive. If he is in that approximately 15 percent of the population without it, he is said to be Rh negative.

Whether a person is Rh positive or negative doesn't in itself cause any alarm. The only time there can be cause for concern arises at the time when an Rh¬negative woman becomes pregnant and her partner is Rh¬positive. The developing child of this couple could inherit his father's Rh positive blood and also a condition known as erythroblastosis in which blood cells are destroyed.

This type of destruction happens only if some Rh positive blood becomes intermixed with the mother's negative blood. In such cases, the mother's blood develops antibodies to the condition. These antibodies serve to protect the mother against new materials in her blood. The child of an Rh negative father, on the other hand, would suffer no ill effects.

Since fetal blood does not usually have the opportunity to mix with that of the mother until the moment of delivery, the mother usually doesn't build up antibodies until after the birth of her first Rh positive child. This means her first Rh negative child would not be affected, and this child would run no risk.

At the time of the birth of a baby, doctors always pay special attention to all children of a couple with incompatible blood.

Not all Rh negative women have problems. Studies have shown that only one marriage in eight involves an Rh positive man and an Rh negative woman. Antibodies appear in the blood of only about one woman in 20 of these incompatible couples. With new drugs now being used, this number will become even smaller.

Measures are available to help a baby if antibodies are detected in the mother's blood. Blood transfusions after birth can help minimize the anemia and jaundice that can occasionally afflict the baby. Induced labor can cut down the time the baby is exposed to the mother's antibodies, though prematurity may be a problem.

One thing is certain: There is no reason whatsoever, doctors agree, why a woman with Rh negative blood and a husband who is Rh positive should not have children.

 

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