There are approximately 46 Rhesus group red cell surface antigens. C, c
, and patients with the D Rhesus antigen are considered Rh-positive.
Approximately 85% of the white population and 92% of the black population has the D antigen, and individuals lacking this antigen are called Rh-negative. In contrast to the ABO groups, Rh-negative patients usually develop antibodies against the D antigen only after an Rh-positive transfusion or with pregnancy, in the situation of an Rh-negative mother delivering an Rh-positive baby.