Group - Rh disease

Rh disease (also known as Rh (D) disease, 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 (also known as HDN). The disease ranges from mild to severe. When the disease is mild the fetus may have mild anaemia with reticulocytosis. When the disease is moderate or severe the fetus can have a more marked anaemia and erythroblastosis (erythroblastosis fetalis). When the disease is very severe it can cause morbus haemolyticus neonatorum, hydrops fetalis, or stillbirth. During any pregnancy a small amount of the baby's blood can enter the mother's circulation. If the mother is Rh negative and the baby is Rh positive, the mother produces antibodies (including IgG) against the Rhesus D antigen on her baby's red blood cells. During this and subsequent pregnancies the IgG is able to pass through the placenta into the fetus and if the level of it is sufficient, it will cause a Rhesus D positive fetus to develop Rh disease. The mechanism is maternal anti-D IgG passing through the placenta to the fetus causing destruction of fetal red blood cells. Generally Rhesus disease becomes worse with each additional Rhesus incompatible pregnancy. The main and most frequent sensitizing event is child birth (about 86% of sensitized cases), but fetal blood may pass into the maternal circulation earlier during the pregnancy (about 14% of sensitized cases) . Sensitizing events during pregnancy include miscarriage, therapeutic abortion, amniocentesis, ectopic pregnancy, abdominal trauma and external cephalic version.