There is no HR-negative blood, it should be RH-negative blood.RH blood type is one kind of human blood type, there are two kinds of RH blood type, one is RH-positive and the other is RH-negative.RH-positive is the one which contains D-antigen on the membrane of the red blood cell, and the one which doesn’t have D-antigen on the membrane of the red blood cell is RH-negative. In China’s Han population, RH-positive people account for the vast majority, RH-negative people are very few, at the same time, due to the D antigen has a strong antigenicity, can stimulate the body to produce antibodies, RH-negative people who receive RH-positive blood, will produce a high concentration of antibodies, the antigen-antibody reaction occurs, resulting in the occurrence of hemolytic reaction. Meanwhile, RH-negative women usually do not experience hemolytic reaction when they give birth to their first child, but when they give birth to their second child, they are prone to severe hemolytic reaction.