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Rh Factor Incompatibility and How it Affects a Pregnant Mother and Her Fetus or Newborn Rh incompatibility is a condition that occurs when the mother of a fetus or a newborn has Rh-negative blood type and the fetus or newborn has Rh-positive blood. This incompatible blood reaction may cause progressive problems in a newborn as well as life-threatening problems for future pregnancies. What is the Rh Factor? Rh factor is a protein present in red blood cells. Proteins called antigens on the surface of the red blood cell (RBC) determine the type of blood you have (Ackley and Ladwig 98). There are four major blood types: A, B, AB, and O. There are two antigens, A and B. When A antigen is present, you have Type A blood. If you have the B antigen on the RBC, then you have the Type B blood. When both A and B antigens are present, you have Type AB blood. When neither are present, you have Type O blood. When an antigen is present on the RBC, then the opposite antibody is present in the plasma. For instance, Type A blood has anti-Type-B antibodies. Type B blood has anti-Type-A antibodies. Type AB has no antibodies in the plasma, and Type O blood has both anti-Type-A and anti-Type-B antibodies in the plasma. These antibodies are not present at birth but are formed spontaneously during infancy and last throughout life. In addition to the ABO blood group system, there is an Rh blood group system. There are many Rh antigens that can be present on the surface of the RBC. The D antigen is the most common Rh antigen. If the D antigen is present, then that blood is Rh+. If the D antigen is missing, then the blood is Rh-. This Rh factor is connected to a person’s blood type. For example, your blood may be AB+ which means that you have Type AB blood with a positive Rh factor. Unlike the ABO system, the corresponding antibody antigen does not develop spontaneously but only when the Rh-person is exposed to the antigen by blood transfusion or during pregnancy. Who is Affected by This Disease? Rh factor, like the blood types, A, B, and O, is inherited from one’s parents. Through a simple blood test, blood type and the presence of the Rh factor can be determined. About 85% of white Americans, 95% of African Americans, and 99% of Chinese have the Rh protein in their blood (Sahagun 1). People easily inherit it because its presence is dictated by a dominant gene. The Rh factor affects about one in a hundred pregnancies. Rh factor is important only during a pregnancy in which an Rh-negative woman is carrying an Rh-positive fetus. This can occur when an Rh-negative woman conceives a baby with an Rh-positive man. The gene for Rh-positive blood is dominant over the gene for Rh-negative blood, so their baby will be Rh positive.
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