The Rhesus, or Rh factor, is a protein that's present on the red blood cells of about 85 percent of all people. The 15 percent who don't have the protein marker are considered Rh negative. Generally, the presence or lack of the Rhesus factor has no impact on health. The only potential problem occurs if an Rh negative woman is pregnant with a baby who has Rh positive blood, which can happen if the father of the child is Rh positive.

Rh Incompatibility

Rh incompatability is not always predictable. The baby's Rh status is not usually determined until after it is born, and a father with Rh positive blood can still transmit a recessive Rh negative gene. If the unborn baby is Rh positive, the Rh negative mother's body will build antibodies to the baby's blood, which attack the developing fetus and result in anemia. This can manifest as a decrease in the baby's growth rate or movement. If left untreated it could lead to neurological damage, underdevelopment of lungs, kidney and brain, or stillbirth.

Treatment

Rh incompatibility can be treated best if identified early. A shot of Rh immunoglobulin, called RhIg or RhoGAM, around the 28th week of pregnancy, can prevent the mother's body from becoming sensitized to the Rh factor in the babies blood. This will suppress the production of antibodies and prevent any adverse effects. Usually, the mother will have another shot after delivery, miscarriage, ectopic pregnancy or abortion to prevent the development of antibodies to any Rh positive cells she might have received from the baby. Development of such antibodies could affect future Rh positive pregnancies.

Late Detection

Early blood tests of both the mother and father can alert doctors to the potential risk of Rh incompatibility, and such screening is an essential part of effective treatment. Once the mother's body has developed antibodies to the Rh factor, RhoGAM treatment is no longer effective. Close monitoring of the fetus' development becomes necessary to monitor for symptoms of Rh incompatability. If the condition is severe, blood transfusions can be attempted in utero, or labor can be induced to prevent further harm to the baby.

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