Rh factor: Meaning and Definition of

Rh fac•tor

1. any of a type of specific antigen present on the surface of red blood cells, persons having inherited such antigens being designated Rh+and persons lacking them, a much smaller group, being designated Rh−blood of Rh− persons is incompatible with Rh+ blood because of antibody reaction, and an Rh− woman who bears an Rh+ baby will have formed antibodies to the fetal blood that, unless removed from her bloodstream by apheresis in a subsequent pregnancy, will be carried across the placenta and destroy red blood cells of the next Rh+ fetus, resulting in erythroblastosis in the newborn.