What is the Rh factor?
There are five antigens in the Rhesus blood group system: D, C, c, E and e. The main characteristic is the Rhesus factor D (Rh factor). If a person carries this factor on the surface of his red blood cells (erythrocytes), he is Rh-positive; if the factor is missing, it is called Rh-negative.
Researchers discovered the rhesus factor in the 1940s: they took blood from rhesus monkeys and injected it into guinea pigs. They then administered the rodents’ serum to the rhesus monkeys and observed that the monkeys’ erythrocytes clumped together: the rodents had formed antibodies in their blood against the monkey erythrocytes, which attacked the monkeys’ erythrocytes after transfer to their bodies.
Rhesus factor: significance for pregnant women
If the mother becomes pregnant again with an Rh-positive child, the mother’s antibodies enter the fetal bloodstream. There, they destroy the red blood cells of the fetus – doctors refer to this as “haemolyticus neonatorum”: In the unborn child, effusions develop in the pericardium and pleura, and heart failure can result.
To prevent this from happening, the doctor administers Rh factor prophylaxis to an Rh-negative mother shortly after the birth of an Rh-positive child. This prevents the formation of the antibodies, so that there is no danger for a second pregnancy with an Rh-positive child.
