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What is Rh disease?

Rh disease is a potentially dangerous form of anemia that can develop in fetuses whose mothers have Rh-negative blood. The Rh factor is a protein molecule found on the surface of red blood cells. Problems can occur if a mother has Rh-negative blood and her baby has Rh-positive blood and the baby's blood enters the mother's bloodstream. The mother's immune system may recognize the baby's blood as foreign and create antibodies to the baby's Rh-positive blood, a process known as Rh sensitization. If those Rh antibodies cross the placenta to the fetus during pregnancy, the antibodies may destroy some of the fetus's red blood cells, resulting in anemia or Rh disease.

Although Rh sensitization can happen during a first pregnancy, it usually won't happen until the end of the pregnancy, during labor and delivery, when the baby's blood mixes with the mother's blood. For this reason, firstborn babies are at much lower risk of Rh disease than second, third or later pregnancies. If the Rh incompatability happens in a second or later pregnancy, the mother's antibodies may recognize the Rh factor early in the pregnancy and be prepared to attack the baby's Rh-positive blood cells.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.