Epidemiology
In Germany and Central Europe, about 83% of the population is rhesus positive, which may lead to shortages of suitable transfusion blood for rhesus negative recipients of blood donations. The situation for rhesus-negative recipients is even more critical in Eastern Europe, where some of them represent only 4% of the population.
Clinical significance
The most important significance of the rhesus system lies in the classification of blood transfusions and in the dangerous disease haemolyticus neonatorum, a disease of the child in the womb in which the mother produces antibodies against the blood of the foetus. The Rhesus system occupies a similar position in the classification of blood for transfusions as the AB0 system. It is important to ensure that a rhesus negative does not receive rhesus positive blood, as complications can occur.
The formation of antibodies against the rhesus D protein, which can damage the embryo during pregnancy, is also important here. Conversely, a rhesus-positive donor has nothing to fear if he is transfused with rhesus-negative blood, since there is no rhesus factor on the donated blood cells against which he could form antibodies. Morbus haemolyticus neonatorum can occur when a rhesus-negative mother who has produced antibodies against the rhesus factor is pregnant with a rhesus-positive child.
Due to the above-mentioned inheritance, it is possible that a child of a rhesus negative mother becomes rhesus positive through a rhesus positive father. When the rhesus-positive child is born, sufficient amounts of the child’s blood can enter the mother’s circulation to build up an immune reaction (similar to a vaccination) against the rhesus factor. Theoretically, it is also possible to build up a rhesus immunity by giving a rhesus-positive blood sample to the mother, which is why very strict regulations apply here.
During pregnancy with a Rhesus-positive child, the newly formed antibodies of the mother find their way into the child’s circulation. There they lead to the dissolution of the embryo‘s red blood cells and can cause severe damage to the embryo. As a precautionary measure, a mother can be administered drugs during the first birth of a rhesus-positive child to prevent the development of immunity to the rhesus factor.