 [ Symptoms ] i have a porcelain veneer bridgework and one crown can they be damaged by over the counter whitening products [ Disease ] a blood type test categorizes your blood according to the major human blood group abo system a person is abo type depends upon the presence or absence of two genes — the a and b genes these genes determine part of the configuration of the red blood cell surface possible abo blood groups include o a b or ab the rh antigen is another compound that may or may not be present on the surface of red blood cells the rh test determines whether this configuration is present rh positive or absent rh negative on an individual is blood cells rh testing is performed because the difference in rh blood group types between an rh negative mother and her rh positive baby can lead to hemolytic disease a severe condition in which there is breakdown of the red blood cells in the newborn if an rh negative mother carries an rh positive fetus she may develop antibodies against the rh component of the baby is red blood cells these antibodies could cause hemolytic disease of an rh positive baby in subsequent pregnancies prevention of hemolytic disease of the newborn is carried out by giving rh negative mothers rho d immune globulin brand name rhogam after delivery of an rh positive baby this prevents the mother is immune system from reacting to the rh positive blood of any subsequent fetus