Blood Group Incompatibility

Everyone's blood is one of four major types: A, B, AB or O. Blood types are determined by the types of antigens on the blood cells. Antigens are proteins found on the surfaces of blood cells that can type B has only B antigens, type AB has both A and B antigens, and type O has neither A nor B antigens. There are other antigens, referred to as minor, that can make blood types even more specific. One of the most common of these minor antigens is the Rh factor.

As a part of your prenatal care, you will have blood tests to find out your blood type. If the mother's blood lacks the Rh antigen (Rh negative), and father's blood contains it (Rh positive), the fetus can acquire the antigen from its father. This can result in the mother's blood being incompatible with the blood of the fetus.

Normally, during pregnancy a small amount of the fetus's blood mixes with the mother's blood. When the fetus's blood is different allergic to the fetus by making antibodies to the antigens in the fetus's blood. This process is called sensitization. If the antibodies the mother produces cross the placenta into the fetus's bloodstream, the mother's antibodies attack the fetus's blood, breaking down its red blood cells and causing anemia. This is a serious condition called erythroblastosis fetalis, also known as hemolytic or Rh disease. It can become severe enough to cause serious illness or even death in the fetus or newborn.

One of the main causes of this disease-sensitization to the Rh factor- acan usualy be prevented. One antibodies are formed, they do not go away. Therefore, the best course is to prevent the mother from becoming sensitized, and thus forming antibodies, in the first place. To so this, your doctor will prescribe Rh immunoglobulin (RhIg) injections if you are unsensitzed.

If you have already become sensitized, your fetus is at risk. As your pregnancy progresses, your doctor will measure the levels of antibodies in your blood. If the levels become high, special tests may be done to check your fetus's health.

If the fetus is anemic, it will need a blood transfusion. After 18 weeks of pregnancy, these transfusions can be given during pregnancy while the fetus is still in the uterus. If the fetus is old enough to be delivered, your doctor may decide on early delivery, and the baby can be treated in a special-care nursery.