RHD blood type positive means that a person’s blood type is RH positive in the RH blood type system. The RH blood group system is determined by the presence or absence of the D antigen on the red blood cell membrane, with those containing the D antigen being RH-positive and those not containing the D antigen being RH-negative. Since the D antigen is a very strong antigen that stimulates the body to produce the corresponding antibodies, the RH blood group is of great importance in clinical blood transfusion and obstetrics. For example, RH-negative people can only receive RH-negative blood, and serious hemolytic reactions may occur if RH-positive blood is transfused. Similarly RH-negative women usually do not have hemolytic reactions when they give birth to their first child; however, when they give birth to their second child, severe neonatal hemolysis can easily occur.