Rh factor plays a crucial role in child's birth born out of a marriage between woman and a man. In such a case, the mother becomes sensitive while carrying a first child within her womb. The reason for such sensitivity is that some of the RBCs from the developing embryo get into the blood stream of the mother during development, causing her to produce anti-Rh antibodies. In fact, the first child of such parents is nearly normal and is delivered safely. However, if such a mother gets pregnant again, the subsequent fetuses will be exposed to the anti-Rh antibodies produced by the mother. As a result serious damage to the red blood cells of the developing embryo will occur causing haemolytic disease of the newborn (HDN) or erythroblastosis fetalis. This disease leads to the death of the developing embryo before birth or after parturition.