Rh incompatability is a state which arises when a pregnant woman is Rh negative and her unborn child is Rh positive. What problem arises in this we can understand in this way. In some cases there can be some feto-maternal haemorrhage or there can be mixing of maternal and foetal blood. Then some of the fetal RBC which is Rh positive will enter into the maternal circulation. Since the mother is Rh negative she doesn’t have that antigen and hence our immune system will trace that antigen which is a foreign body for her and will start producing antibodies for her. If the foeto-matrernal bleeding is small then there will be reaction of antigen-antibody and it will destroy then and there. But if feto-maternal haemorrhage is more than some of these antibodies will be entering into the fetal circulation and these antibodies can cause destruction of the fetal RBCs which can cause fetal anaemia, jaundice of varying severity, hepatospleenomegaly or the kernicterus which is a brain damage. In severe cases of RH immunisation in consecutive pregnancies we can see the disease status like erythroblastosis foetalis. Normally there are three stages in pregnancy where there can be some mixing of blood, like one at 12 weeks, 28 weeks, and maximum it happens around or at the time of delivery. So first born child is normally not affected because duration of exposure is very minimal. But if in consecutive pregnancy if the foetus is Rh positive then the chances of extent of damage is more. So to avoid this situation we have to immunise the woman with a passive immunity. There acn be other conditions also where there can be mixing of blood like in cases of spontaneous or induced abortion, if a woman gets bleeding in pregnancy or if theer is invasive procedures like chorionic villus sampling or amniocentesis. So prevention is the main stay of management of the Rh incompatability. So once the woman is Rh negative, husband is Rh positive we just test them with indirect Coombs test which can assess the feto-maternal bleed and if it is found to be negative which we do at 12 weeks, 28 weeks, then we immunise the woman after 28 weeks with injection anti D or immunoglobulin 300 microgram. If there is a history of abortion or anything we can immunise them earlier also. If it is below 12n weeks we can immunise them with 150 micrograms. If it is after 12 weeks we can immunise them with 300 micrograms. Once again the baby is delivered we check for the baby’s blood group and we do. If the baby is fine Rh positive once again immunisation is given with anti D immunoglobulins. These are actually fighters. If further feto maternal haemorrhage happens it will fight against that. In severe cases when the Rh iso-immunisation has already happened we can assess the pregnancy with estimation of Rh antibody titre and these babies are at a risk so very careful monitoring is required for these babies and they are given intrauterine transfusion with blood or exchange transfusion is done and early delivery is indicated.
