Rh Factor



What is the Rh factor?

          The term Rh factor stands for Rhesus factor. In biology, it is known as a group of antigens, which exists in the red blood cell of human beings. Karl Landsteiner discovered the Rhesus system in 1940 while doing research on Rhesus monkeys regarding blood groups. The Rhesus factor in human involves reaction with the blood of presence of absence of certain substances or factor in the red blood cells. There are half a dozen Rhesus factors, but D factor is especially in a majority of people and they are known as Rhesus positive (Rh+). About 15% of the human population however inherits blood that lacks this Rhesus factor. Their Rh factor is thus described as Rhesus negative (Rh-).

          There is no naturally occurring anti-Rh antibody. But if by mistake Rh+ blood is transfused into an Rh- person’s system, it can stimulate production of an antibody against the foreign D factor and this antibody may eventually destroy the donated cells. The reaction is very slow in the first transfusion, but becomes fierce in the second or subsequent ones.

          The Rh factor plays a significant role during pregnancy. Some or all the children of an Rh- mother and an Rh+ father may inherit the factor from the father. When an Rh- mother conceives a Rh+ baby, and the blood supplies of the mother and the baby mix during the delivery resulting in some of the baby’s blood mixing with the mother’s blood, her blood may form antibodies against the Rh+ factor. Although these antibodies disappear after a few months, the mother is sensitized. I subsequent pregnancies, she may produce ant-Rh bodies, which would attack the baby’s red cells. As a result, the child might be still-born or may die at birth due to a heart failure or a damaged brain or jaundice. In extreme cases, many red blood cells are destroyed and the baby may die before birth.

          It is possible to overcome the problem with an exchange transfusion, the gradual removal of the baby’s blood, a few milliliters at a time, and its replacement with Rh- blood. In this way, some 95% of the affected babies can be saved.

          The condition brought about by the Rh incompatibility is known as hemolytic disease of the neonate. The risk has been lessened by the development of a vaccine made form the anti-Rh antibody known as Rh immune globulin. If this is administered to the mother with 24 hours of the birth of a Rh+ baby, it removes form her blood any Rh+ cell, which may have seeped in. this saves her from becoming sensitized.

          The vaccine is now given s a preventive measure to the Rh- mother and it is repeated in each pregnancy. Due to these precautions, therefore, the number of deaths of newborn babies caused by hemolytic disease is falling rapidly.

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