Is their such a thing as blood d?
I assume what you are talking about is D antigen in Rh (Rhesus)
blood group system. Rh blood group system is the most important
blood group system after ABO blood group system (i.e. type A (AA,
AO), type AB, type B (BB, BO), type O (OO) ).
The Rh blood group system consists of 50 defined blood-group
antigens and the 5 antigens D, C, 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. Rh factor (Rh- and Rh +
depending on D antigen neg/pos) is important for blood transfusion
and prevention of hemolytic disease of the newborn or
erythroblastosis fetalis (basically the baby and mom have different
blood type - Rh- and Rh+ and cause severe immune response - fatal
to the newborn)