The most common problem with blood types between a mother an fetus occur when the mother has a different Rh blood type than their fetus. Interestingly enough, this is not a problem with the mother’s first pregnancy but can cause problems with future pregnancies. We will walk through an example of why this is a problem in order to illustrate why differences in Rh factor D are not typically problematic during a first pregnancy but can have serious consequences for future pregnancies.
If a fetus receives one Rh+ gene from their father an one Rh- gene from their mother then that fetus will be Rh+. Within the womb the fetus actually has their own separate blood supply from the mother that is carrying it so the mother will not immediately develop Rh+ antibodies unless there is some sort of internal trama to the fetus while in utero. However, when the child is born there is a lot of blood exchange between the mother and the fetus and inevitably the mother will be exposed to the fetus’s Rh+ blood, whereby she develops an antibody to that factor D antigen. The baby that has already been born will not be affected to by this fact however, if the mother has another infant that is born Rh+ there could be dire consequences.
If a mother with the Rh+ antibody has a fetus that is Rh+, the fetus will develop hemolytic disease of the newborn. This disease is caused by the fact that the mother’s anti-Rh factor D antibodies cross the placenta and enter the fetus’s body. Once inside the antibodies will attach to and destroy most of the fetus’s red blood cells, robbing their cells of the oxygen that blood carries. Without serious medical intervention, the fetus will not survive at this point. So what can be done about this rather common problem?
Today, mother’s that are O- are commonly given a shot called Rhogam which prevents the mother’s blood from coming into contact with the fetus’s Rh factor D antigens. Without coming into contact with those antigens the mother will never develop the anti-Rh antibodies that can be so deadly to followup pregnancies. This solution is simple and effective but it also makes yet another good case for good physician lead prenatal care.