Blood typing is done before a blood transfusion or when a person's blood is classified for donation. Blood typing is a painless and quick way to ensure that you receive the correct blood during surgery or after an injury. Blood clumping, also known as agglutination, can be dangerous if incompatible blood is used.Blood type is extremely important for pregnant mothers. If the mother is Rh-negative and the father is Rh-positive, the child will most probably be Rh-positive. A drug known as RhoGAM must be given to the mother in these conditions.This medication will prevent her body from producing antibodies that could attack the baby's blood cells if their blood is mixed during pregnancy, which is common.