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Chapter 7 Hemolytic Disease of the Newborn, , , , First Pregnancy, , RH+ Fetal, blood, , , , Ko, , , , The first child is born, unaffected because the, fetal and maternal, circulation are seperate., , Mother's RHblood, now, with RH, , antiodies, , Maternal Circulation, , , , , , , , , Second Pregnancy, , , , , , , , Fetal RH+ blood is, attacked by maternal, RH antigens, , , , Fig. 7.1 The process of the development of Erythroblastosis fetalis through RH incompatability., , Erythroblastosis fetalis, , Erythroblastosis fetalis, is an alloimmune condition, that develops in a fetus, when the IgG molecules, (one of the five main types of antibodies) produced, by the mother pass through the placenta. Among, these antibodies are some which attack the red, blood cells in the fetal circulation; the red cells are, broken down and the fetus can develop reticulocytosis and anaemia. This fetal disease ranges from, mild to very severe, and fetal death from heart, failure (hydrops fetalis) can occur. When the, disease is moderate or severe, many erythroblasts, are present in the fetal blood and so these forms of, the disease can be called erythroblastosis fetalis, (or erythroblastosis foetalis)., , Antibodies are produced when the body is, exposed to an antigen foreign to the make-up of, the body. If a mother is exposed to a foreign antigen and produces IgG (as opposed to IgM which, does not cross the placenta), the IgG will target the, antigen, if present in the fetus, and may affect it in, , Antibodies are produced when the body is, exposed to an antigen foreign to the make-up of, the body. If a mother is exposed to a foreign antigen and produces IgG (as opposed to IgM which, does not cross the placenta), the IgG will target the, antigen, if present in the fetus, and may affect it in, utero and persist after delivery. The three most, common models in which a woman becomes sensitized toward (i.e., produces IgG antibodies, against) a particular antigen are:, , - Fetal-maternal hemorrhage can occur due to, trauma, abortion, childbirth, ruptures in the, placenta during pregnancy, or medical procedures, carried out during pregnancy that breach the uterine wall. In subsequent pregnancies, if there is a, similar incompatibility in the fetus, these antibodies, are then able to cross the placenta into the fetal, bloodstream to attach to the red blood cells and, cause hemolysis. In other words, if a mother has, anti-RhD (D being the major Rhesus antigen) IgG, , , , Page 156