Rh Factor

What is Rh factor?
Every person’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.

Rh describes the factor that is found on the red blood cells of most people. People with the Rh factor are Rh positive, those who do not have the factor are Rh negative. Approximately 85% of the United States population is Rh positive and about 15% is Rh negative. The type we are is determined by our parents just like eye color. The Rh factor does not affect a person’s general health. Rh factor can be determined by a simple blood test which only requires a finger stick.

When is Rh important?
Rh is important when donating blood or receiving a blood transfusion and during pregnancy. Rh negative blood donors are always in demand because Rh negative patients need Rh negative blood. Rh positive patients can receive blood from either Rh positive or Rh negative donors. In pregnancy, Rh is especially important when an Rh negative woman carries an Rh positive fetus.

What if I am Rh negative and pregnant?
If an Rh negative woman is pregnant with an Rh positive fetus, her body will produce antibodies against the fetus’s blood, causing a disease known as the Rh disease. Sensitization to the disease occurs when the woman’s blood is exposed to the fetus’s blood. The antibodies attack and destroy the Rh positive red blood cells of the fetus, a progressive anemia develops and in severe cases, there can be heart failure or even death. This hemolytic disease usually does not affect the first pregnancy, but once a woman has produced antibodies, all future Rh positive pregnancies are at risk. Antibody production can be prevented by giving Rh Immune Globulin (Rhlg or RhoGam).