Erythroblastosis foetalis is caused when mother is
Erythroblastosis foetalis also called the haemolytic disease of the newborn. It is a type of anaemia in which the red blood cells (erythrocytes) of a fetus are destroyed in a maternal immune reaction resulting from a blood group incompatibility between the fetus and its mother. Symptoms of erythroblastosis fetalis range from mild to severe; death of the fetus or newborn sometimes results. When an Rh− mother is impregnated by an Rh+ father and is carrying an Rh+ baby, the fetus Rh antigens will be perceived as foreign invaders in mother's body. It can initiate the protective mechanism that can end up harming the child. During first pregnancy, the antibodies are produced in lower concentration and does not harm the fetus. But antibodies against the Rh factor will be produced in the mother's body during delivery of first child. During second pregnancy with Rh+ baby, concentration of antibodies against Rh factor will build up, which will attack the blood cells of fetus and will cause its death (Erythroblastosis foetalis). Thus, the correct answer is option C.