Besides the ABO system, the rhesus system is another important blood group system. In the rhesus system, there are several antigens attached to red blood cells: Rh factors (Rh factors).
In humans, Rh factors C, D, E and c, d, e are included .
Being Rh positive means that red blood cells have on their surface a D antigen. Rh negative does not have it.
As in the ABO system, in the Rh system, there may be incompatibility between the blood groups of two individuals carrying different Rh factors. This incompatibility is important, particularly in the case of blood transfusion or during pregnancy.
Again, tests are performed before performing a blood transfusion to ensure that there is no rhesus incompatibility.
The Rh system and pregnancy
To understand the issues of the Rh system in the blood group during pregnancy, let's look at the different cases:
> If a woman is Rh negative (about 15% of women in France) and the child she wears is also Rh negative, there is no problem.
> If a woman is Rh negative and the child she is wearing is also Rh positive, there may be a fetoma-maternal immunization. The child's red blood cells can enter the mother's bloodstream at the placenta. The mother can then produce irregular anti-Rh clusters. Thereafter, there may be a risk for the next pregnancy ... Indeed, if the mother expects another child Rh positive, agglutinins (antibodies) made by the mother will destroy the red blood cells of the fetus.
To avoid this kind of problem, which can be very serious, if the mother is Rh negative and the fetus Rh positive, the mother is given anti-Rh blood gammaglobulins that will destroy the few red blood cells passed in the mother's circulation. .
This arrangement is usually taken at the beginning of the 3rd trimester of pregnancy, but also in case of amniocentesis, strapping, version of the child from the siege position to the head-down position ... in short as many circumstances that promote the passage of red blood cells from the child to the mother.