1. There are four types of blood group A,B,O and AB.

2. There is one other type of blood group known as Rh factor or Rhesus Monkey factor which is an inherited factor.

3. Most of the people are Rh positive (Rh+ve) which means that the person have Rh factor in them.

4. People who do not have Rh factor are called as Rh negative people (Rh-ve).

5. Rh-incompatibility in humans may lead to a disorder called as Erythroblastosis foetalis.

6. In this disorder, at the time of pregnancy if the foetus is Rh+ve and the mother is Rh-ve and if the blood from foetus enters the mother’s bloodstream, antibodies against the foetus blood is created.

7. At the time of first pregnancy it does not have any affect.

8. But in subsequent pregnancies if the baby is (Rh+ve), the antibodies formed against Rh+ve blood during first pregnancy may enter the foetus through placenta.

9. This may lead to destruction of foetus’s RBC’s which may lead to death of the foetus or extreme Anaemia.