In this country, approximately 83-85% of the population has a protein on the surface of their red blood cells called Rh(D) antigen. These people are known as Rh positive.
The remaining 15-17% do not have the Rh(D) antigen protein and are therefore Rh negative. When a person who is Rh negative has Rh positive erythrocytes introduced in their blood circulation (following a transfusion, or in pregnancy) their body may respond by manufacturing anti-Rh antibodies in order to destroy the Rh-positive erythrocytes.
If the unborn child of an Rh-negative pregnant woman is Rh positive, some red blood cells from the child can be passed to the mother’s blood via the placenta. Although this can happen at any stage during pregnancy, it is more common after the 28th week, during birth or during a termination.
The mother’s immune system can respond with an immune response whereby it makes anti-Rh antibodies which cross the placenta and attack the Rh-positive child’s erythrocytes or, more frequently, attack the erythrocytes of a second Rh-positive child, causing the destruction of the erythrocytes. This then causes the unborn child to develop anaemia and an excess of bilirubin in the newborn which is very dangerous for its neurological toxicity. This is known as haemolytic disease. The most serious cases can result in death.
Administering anti-Rh(D) immunoglobulin to the mother soon after exposure to the child’s Rh-positive blood, suppresses the mother’s immune response and avoids the foetus becoming ill. Systematic administration of anti-Rh(D) immunoglobulin in such cases from the end of the 1960s in all Rh-negative women with Rh-positive foetuses has almost eradicated an illness which, in 1969, killed 48 unborn children per 100,000 live births.
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