Rh Incompatibility

Definition - What does Rh Incompatibility mean?

Rh incompatibility occurs when a pregnant mother has Rh-negative blood, but her fetus has Rh-positive blood. Rh incompatibility may cause miscarriage, recurrent pregnancy loss (RPL), and complications with childbirth. This condition can be life-threatening for the mother and fetus if not diagnosed and properly treated. A woman with Rh-negative blood will need to pursue treatment for every pregnancy she conceives.

FertilitySmarts explains Rh Incompatibility

Rh-positive and Rh-negative refer to something called Rh factor, a protein found in red blood cells. A person is born with his or her Rh factor type and Rh factor is hereditary, passed down from parents to children. Most people are Rh-positive. Rh factor does not impact health, except in the case of pregnancy.

When a mother has Rh incompatibility, it means that her blood Rh factor is different then her baby’s. During pregnancy, a fetus’ blood stream may cross with the mother’s. When this occurs, the mother’s body does not recognize the foreign cells, and reacts by creating antibodies against the baby’s Rh-positive blood. Antibodies are the body’s standard way of protecting against any foreign “invading” cells, an important part of the body’s immune system. Antibodies are what keep human bodies healthy.

However, in this case, the antibodies may cross through the placenta, and attack the fetus’ red blood cells. This can be dangerous for both the mother and the baby. The most common result is a condition called hemolytic anemia, where red blood cells are destroyed faster then they are created. This can lead to long-term health complications or death of the fetus.

Many Rh negative mothers may not experience any complications during her first pregnancy. This is because the body has only experienced limited exposure to the "foreign" cells of the fetus. However, during childbirth, the mother and baby's blood come into contact. At that point the mother's body begins developing antibodies to fight the foreign cells. When a later pregnancy is attempted, the antibodies already exist, specifically designed to fight the cells creating the fetus. This can lead to secondary infertility or reccurent pregancy loss (RPL).

Rh incompatibility is completely avoidable. Once detected, medication can be provided in order to prevent the condition. Early prenatal care is an important component of avoiding Rh incompatibility, as early testing can detect Rh-factor blood type. Medication called Rh immune globulin is often prescribed to Rh-negative women who are pregnant.
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