What is Rh isoimmunization?

Rh disease (also known as Rhesus isoimmunisation, Rh (D) disease, Rhesus incompatibility, Rhesus disease, RhD Hemolytic Disease of the Newborn, Rhesus D Hemolytic Disease of the Newborn or RhD HDN) is one of the causes of hemolytic disease of the newborn (HDN). The disease ranges from mild to severe, and typically occurs only in some second or subsequent pregnancies of Rh negative women where the fetus's father is Rh positive, leading to a Rh+ pregnancy. During birth, the mother may be exposed to the infant's blood, and this causes the development of antibodies, which may affect the health of subsequent Rh+ pregnancies. In mild cases, the fetus may have mild anaemia with reticulocytosis. In moderate or severe cases the fetus may have a more marked anaemia and erythroblastosis fetalis (hemolytic disease of the newborn). When the disease is very severe it may cause hydrops fetalis or stillbirth.

Rh disease is generally preventable by treating the mother during pregnancy or soon after delivery with an intramuscular injection of anti-RhD immunoglobulin (Rho(D) immune globulin). The RhD protein is coded for by the RHD gene. James Harrison, OAM, also known as the Man with the golden arm, is a blood plasma donor from Australia whose unusual plasma composition has been used to make a treatment for Rhesus disease. He has made over 1000 donations throughout his lifetime, and these donations are estimated to have saved over two million unborn babies from the condition.