well, first you have to understand about Rh stuff. It's really ALL about the blood. In an Rh(-) (no Rh protein markers on the red blood cell (RBC)) mom with an Rh(+)--(Rh protein markers on RBC) fetus, during the first pregnancy there is usually little danger unless there are complications during preg. Usually though, when being born, the blood mixes a little and the Rh- mom begins to develop antibodies to the Rh+ blood. If mom gets pregnant again with an Rh+ baby, she already has antibodies to the protein markers on her baby's RBC. The antibodies pass through the blood barrier of the placenta, on search and destroy mode. When they find the RBC in the fetus, they cause the RBCs to either clump together (clot and die) or they destroy them. The result of this incompatibility ranges from fetal anemia, jaundice (caused by breakdown of RBC and the body's inability to deal with bilirubin as a by-product of RBC death,) and edema (inability of tissues to rid themselves of excess water,) to brain damage, liver failure and fetal death. It tends to get worse with each successive pregnancy, usually by the 3rd or 4th, fetal death is almost assured if the mother has refused treatment.
Rh antibody injections (antibodies are white blood cells) are usually given to the Rh(-) mother soon after delivery of an Rh(+) baby. The antibodies "trick" the mother's immune system into thinking they have won the war. Thus the mother's own immune system never learns to make the antibody to the Rh+ antigen. In addition, since the Rh antibodies are already there by injection, they recognize the baby's blood in the mother's system and destroy those cells before the mother's own system recognizes them and fires up her own immune system.
The Rh factor injection is made specifically from blood components (just like the clotting factor VIII, and XIII given to hemophiliacs) and is rejected by many as "transfusion."
Personally, I find it ironic that the Patriarchal WTS approved the use of VIII and others for hemophilacs--an affliction manifested by males, many years before "allowing" the use of Rh factor antibodies for pregnant women.