All blood is either rhesus-negative or rhesus-positive. A routine blood test at the beginning of the pregnancy will show whether you are rhesus-positive or negative. You run a risk of rhesus incompatibility in pregnancy only if you have a rhesus-negative blood group while your husband has a rhesus-positive blood group. There is no symptom of rhesus incompatibility that you will notice.
A rhesus negative mother could either bear a rhesus positive foetus or a rhesus negative foetus.
If a rhesus-negative mother bears a rhesus-positive foetus, some of the baby’s red cells may leak into mother’s blood circulation. This is most likely in late pregnancy or at the time of delivery. The body responds to the baby’s blood as it would to an invader and the natural defence mechanisms will produce antibodies against it. If these antibodies leak back to the baby’s circulation, they can destroy a large number of the baby’s blood cells. In order to avoid this from happening, an injection of anti-D immunoglobulin is given to a rhesus-negative mother immediately after the birth of a rhesus-positive baby.
This injection is to be given within 48 hours after the birth of the baby. It stops the mother’s biological defence mechanism from acting against the foreign rhesus substances. A fresh injection is given after every delivery, miscarriage or abortion.
If anti D injection is not given, mother’s antibodies damage the blood cells of any rhesus-positive baby carried in future. The antibodies can vigorously attack the baby’s blood so that the baby might get anaemia, jaundice or brain damage and may not survive. If a rhesus negative mother delivers a rhesus negative child, the mother’s body is undisturbed by the leak of negatively cells from this baby at delivery and therefore, the anti-D injection is not needed.
When a rhesus negative mother delivers, the baby’s blood group must be determined soon after birth to decide about administration of anti-D injection.
