Everybody has a blood type. Sometimes a mother-to-be's blood type is a bad match with her unborn baby's blood type. When this happens a problem arises concerning the Rhesus, or Rh, factor that's called Rh incompatibility.
There are four different blood types. They are type A, type B, type AB and type O. Each of these can be either positive or negative.
If you're Rh positive, your blood has a protein on the surface of their red blood cells, or RBCs. If you are Rh negative, your red blood cells will not have such a protein.
About 85 percent of people are Rh positive. This means about 15 percent are Rh negative. Problems can arise if a woman is Rh negative and her partner is Rh positive. The unborn child has a 50/50 chance of being Rh positive because of the father's blood type.
The first time a woman in this situation is pregnant, the risk for Rh incompatibility is low. Usually the blood of mother and child does not mix during a first pregnancy. During delivery though, there is the chance of the two different types of blood mixing.
If this happens the mother's blood will start to manufacture antibodies to this foreign element. Rh antibodies can travel across the placenta. The baby's red blood cells become targets.
Subsequent pregnancies will have higher risk for Rh incompatibility. If her unborn child is Rh positive, problems from her antibodies will ensue throughout the pregnancy. The baby's red blood cells will be attacked and the blood count can become perilously low.
Insufficient red blood cells will inhibit the baby's oxygen levels. Hemolytic anemia, where blood cells break down at a rate faster than they can be replaced, can occur. In serious cases, this can be fatal.
Fortunately, all of this can be averted. A woman who might experience Rh incompatibility will be given an Rh immune-globulin injection the first time she is pregnant, at her 28th week then again within 72 hours of having delivered her baby. These injections will prevent the antibodies from being formed in the mother's body.
During a pregnancy, if a miscarriage occurs or a blood transfusion is needed, the two blood types can intermingle.