Rh factor

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Rh factor

blood

Also known as: Rh antigen, Rhesus factor

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Last updated

July 13, 2026

Quick Summary

The Rh factor is a system for classifying blood groups based on the presence or absence of the Rh antigen on red blood cells. Discovered in 1940, the most significant Rh antigen is RhD.

Problems arise when Rh-incompatible blood is transfused. If an Rh-negative person receives Rh-positive blood, their immune system can produce anti-Rh antibodies. Subsequent transfusions of Rh-positive blood can lead to a severe, potentially fatal, reaction where red blood cells are destroyed.

A similar issue occurs during pregnancy if an Rh-negative mother carries an Rh-positive fetus. While the first child may be unaffected, the mother can develop antibodies that attack subsequent Rh-positive fetuses, causing hemolytic disease of the newborn. This condition, erythroblastosis fetalis, can be fatal. Fortunately, treatments like Rh immunoglobulin injections can prevent this immunization and protect future pregnancies.123

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therapeutics
Blood and blood cells
Most individuals are Rh-positive, which means that they have the D antigen of the complex Rh blood group system. Approximately 15 percent of the population lacks this antigen; such individuals are described as Rh-negative. Although anti-D antibodies are not naturally present, the antigen is so highly immunogenic (able…
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Most individuals are Rh-positive, which means that they have the D antigen of the complex Rh blood group system. Approximately 15 percent of the population lacks this antigen; such individuals are described as Rh-negative. Although anti-D antibodies are not naturally present, the antigen is so highly immunogenic (able…
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childhood disease and disorder
Blood disorders
…have circulating antibodies against the Rh factor. These antibodies can cross the placenta and destroy the red blood cells of her Rh-positive fetus. Unless the mother has been sensitized by blood transfusions, her first Rh-positive fetus is normally not affected. This is because her exposure to the fetal red blood…
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…have circulating antibodies against the Rh factor. These antibodies can cross the placenta and destroy the red blood cells of her Rh-positive fetus. Unless the mother has been sensitized by blood transfusions, her first Rh-positive fetus is normally not affected. This is because her exposure to the fetal red blood…
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heterospecific mating
…this is seen when an Rh-negative woman marries an Rh-positive man and has children who are Rh-positive (see Rh blood group system). Frequently the mother develops antibodies to the fetal blood type, which may result in miscarriage, a stillborn child, or a baby born with severe hemolytic anemia or jaundice.…
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…this is seen when an Rh-negative woman marries an Rh-positive man and has children who are Rh-positive (see Rh blood group system). Frequently the mother develops antibodies to the fetal blood type, which may result in miscarriage, a stillborn child, or a baby born with severe hemolytic anemia or jaundice.…
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Rh blood group system
…Rh antigen, often called the Rh factor, on the cell membranes of the red blood cells (erythrocytes). The designation Rh is derived from the use of the blood of rhesus monkeys in the basic test for determining the presence of the Rh antigen in human blood. The Rh blood group…
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…Rh antigen, often called the Rh factor, on the cell membranes of the red blood cells (erythrocytes). The designation Rh is derived from the use of the blood of rhesus monkeys in the basic test for determining the presence of the Rh antigen in human blood. The Rh blood group…
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rhesus monkey
The determination of the Rh (from rhesus) factor in human blood involves reaction with the blood of this monkey, and a rhesus was the first monkey to be rocketed into the stratosphere. The rhesus monkey and other macaques are classified in the family Cercopithecidae (the Old World monkeys).
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The determination of the Rh (from rhesus) factor in human blood involves reaction with the blood of this monkey, and a rhesus was the first monkey to be rocketed into the stratosphere. The rhesus monkey and other macaques are classified in the family Cercopithecidae (the Old World monkeys).
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