The rhesus (Rh) blood group system is one of the major clinically significant systems, the other being the ABO system.
Our Rh factor is determined by the pair of genes inherited from our parents. Rh system blood group consists of blood group antigens.
Antigens D, P, c, E, and e are the most important. The commonly used terms Rh factor, Rh positive and Rh negative refer to the D antigen only.
In Rh negative blood type the D antigen is absent.