Rhnegative

Rhnegative refers to individuals whose red blood cells lack the D antigen of the Rh blood group system. The Rh system includes several antigens, with D being the most clinically significant. People inherit two copies of the RHD gene; if both copies are nonfunctional or absent, they are Rh-negative, whereas having at least one functional copy typically results in Rh-positive blood. The D antigen is highly immunogenic, so exposure to Rh-positive blood can trigger the formation of anti-D antibodies in an Rh-negative person.

Rh-negative status varies among populations. About 15% of people of Northern and Western European descent are Rh-negative, with lower frequencies observed in African, Asian, and Indigenous populations.

In clinical practice, Rh status guides blood transfusion and pregnancy care. Rh-negative recipients are generally given Rh-negative red blood cells to avoid sensitization. Rh incompatibility between an Rh-negative mother and an Rh-positive fetus can lead to hemolytic disease of the newborn if not managed. To prevent maternal sensitization, Rh-negative pregnant individuals are routinely given Rh immune globulin during pregnancy and after procedures that may mix fetal and maternal blood.

Rh negativity was named after the rhesus monkey, from which the D antigen was first characterized in the 1940s by Landsteiner and Wiener. The term denotes the absence of the D antigen, not a disease state, and forms part of a broader set of Rh antigens.