Blood Type Rh

Definition - What does Blood Type Rh mean?

Blood type Rh is the name of a blood test used to check for the presence of the Rh antigen in a person's blood. A person may either be Rh positive or Rh negative.

Blood is categorized using two typing tests. The first is the ABO test. This test detects the presence of the A and B antigens. Classification is made based on whether one, both, or neither antigen is present. This classification is then further delimited by the presence or absence of the Rh antigen.

Like A or B antigens, the Rh antigen, or Rh factor, is found on the red blood cells. Once tested, the Rh designation is made by describing the blood type as positive or negative. Thus, a full blood type description of someone with type A blood and the presence of the Rh factor, would be A positive. A person with AB blood but no Rh antigen would be classified as AB negative.

The blood type Rh test is also called a Rh blood type test, or an Rh factor test.

WorkplaceTesting explains Blood Type Rh

Determining a person's Rh blood group using blood type Rh testing is common when blood is being donated or transfused. Additionally, women who become pregnant usually undergo and Rh blood test early in their pregnancy. This testing is necessary because blood that is Rh negative will quickly produce antibodies when exposed to the Rh antigens in Rh positive. For blood transfusions, this antibody production can result in what is called a hemolytic transfusion reaction (HTR).

In pregnancy, a problem may arise if a fetus is Rh positive, but the mother is Rh negative. In this case, the mother's blood will develop anti-Rh antibodies that may attack the baby's red blood cells during development.

This condition is called Rh sensitization. In most instances, a first pregnancy in which the incompatibility occurs does not cause harm to the infant. But, if the mother who is Rh negative becomes pregnant again with a Rh positive child, the antibodies then present in her blood will cause harm to the baby. To reduce the chance of future complications, women who are Rh negative are given a preventive shot during their first pregnancy. This immunoglobulin shot prevents Rh sensitization.

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