The Rh is a part of a person's blood type. Blood from a fetus can get into the mother's blood during an abortion. If the mother has a Rh-negative blood type, she can form antibodies that destroy the blood cells of the fetus who has a Rh-positive blood type.

A medicine called RhoGAM is used to help prevent this problem. RhoGAM is an antibody that can prevent Rh-negative mothers from developing her own antibodies against Rh factor. Rh-negative pregnant women with vaginal bleeding will need an injection of RhoGAM to block the process.