If the pregnant woman has a negative Rhesus factor (Rh-) and conceives a first Rh-positive child (factor inherited from the father Rh +), a maternal erythrocyte alloimmunization reaction is established. In practice, the Rh- woman's immune system produces antibodies against the erythrocyte antigens of the fetus that it recognizes as foreign to its organism and "sensitizes it". In the occasion of a second pregnancy with an Rh + fetus, the maternal-fetal incompatibility occurs due to the passage of anti-Rh antibodies to the blood of the unborn child and may be the cause of fetal-neonatal haemolytic disease (MEN, also known as fetal erythroblastosis).
Despite the reduction of the incidence of this complication, it is of fundamental importance to perform the typing of the ABO and Rh blood group, also extended to the partner, and the screening with the Coombs test for the detection of anti-Rh antibodies to women who are in the second pregnancy or have undergone wrong transfusions with Rh + blood (now very rare). After delivery, careful monitoring of the newborn is necessary to counteract any problems caused by severe haemolysis reactions.
from an Rh-positive man and conceives an Rh-positive child. In practice, some cells of the maternal immune system recognize the antigens present on the red blood cells of the fetus as foreign and begin to produce antibodies against them, triggering a reaction to eliminate them.
The severity of maternal-fetal incompatibility is variable, as it depends on the type of antibodies and correlates with the concentration of maternal antibodies that are able to cross the placenta. The most severe occurrence is a form of haemolytic anemia, called MEN, which risks cause serious consequences for the unborn child (including jaundice, hepatosplenomegaly, brain damage).
