Q: My blood group is A Rh negative and my husband's is B positive. I have a 4 years old daughter. Her blood group is O negative. After her birth I have not been given any antibody injection. About 2 years back I had a missed abortion. Now I am planning for another child which will be my third pregnancy. I would like to know when should I get the antibody shot, i.e., before conceiving or after conceiving.

A:Rh incompatibility (or Rh disease) is a state in which a woman with Rh-negative blood group is exposed to Rh-positive RBCs leading to the formation of antibodies against this protein (called Rh antibodies). This process of Rh sensitisation can occur when an Rh-negative woman is carrying an Rh-positive baby or if an Rh-negative woman receives blood transfusion containing Rh-positive cells. During pregnancy and delivery, red cells from the baby enter the mothers circulation. Risk is also increased in pregnancies complicated by placental abruption, spontaneous or therapeutic abortion, and toxaemia, as well as after caesarean delivery and ectopic pregnancy. In either case, her immune system is exposed to the Rh antigen (which is ‘foreign’ to her body) and begins producing Rh antibodies. The problem of Rh incompatibility is of clinical importance only in a pregnant woman or if blood transfusion is required. These circulating antibodies in a woman’s blood are otherwise harmless. Most institutions give human anti-D immune globulin (Rh IgG) antenatally to Rh-negative pregnant women. If a woman has been already sensitised, she needs to get the antibody titres estimated and be closely monitored during pregnancy. Babies born to such mothers too may require specialised neonatal care. Pregnant mothers should have regular indirect antiglobulin tests. As a guide, anti-D antibody levels < 0.2 mg/ml require no action while higher levels require action; levels > 2.0 mg/ml typically are associated with severe disease. Prevention is now carried out with anti-D Ig (intramuscular within 72 hours of delivery) in all Rh-negative mothers giving birth to an Rh-positive child. A Kleihauer test for foetal haemoglobin can be used as a guide for the dose of anti-D Ig to be administered.