Rh Disease (Erythroblastosis Fetalis)

When a mother who is pregnant with a baby whose blood type is incompatible with the baby's, antibodies in the mother's blood may cross the placenta and attack the baby's red blood cells.

This causes anemia in the baby. If it is severe enough, it can cause the baby to die before birth.

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Symptoms

Causes and Risk Factors

This most commonly happens when a woman with Rh-negative blood becomes pregnant by a man with Rh-positive blood and conceives a baby with Rh-positive blood.

Red blood cells from the baby can leak across the placenta into the woman's bloodstream during pregnancy or delivery. This causes the mother's body to make antibodies against the Rh factor.

If the mother becomes pregnant again with an Rh-positive baby, it is possible for her antibodies to cross the placenta and attack the baby's red blood cells.

After birth, an affected newborn may develop kernicterus. This happens when bile pigments are deposited in the cells of the brain and spinal cord and nerve cells are degenerated.

Incompatibilities between ABO blood types can also cause this condition. These are less common than those of the Rh factor and tend to be less severe.

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Diagnosis

During a pregnant woman's first prenatal doctor's visit, she should be screened for blood and Rh type. If she has Rh-negative blood, the father's blood and Rh type should be tested.

If the father has Rh-positive blood and tests of the mother's blood indicate that she hasn't become sensitive to Rh-positive blood, she should be tested again at 18 to 20 weeks of pregnancy and at 26 to 27 weeks of pregnancy.

Depending on the test results, she may need amniocentesis and other tests to measure the levels of bilirubin (a bile pigment) in the amniotic fluid every two weeks starting at 28 weeks of pregnancy. The amniotic fluid surrounds the baby as it grows inside the mother during pregnancy.

Women who are already sensitive to the Rh factor should have amniocentesis at 26 to 30 weeks of pregnancy, depending on how great their apparent sensitivity is.

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Treatments

If monitoring shows that the bilirubin levels in the amniotic fluid are normal, no treatment may be needed as the pregnancy proceeds to delivery.

If the levels are high, showing a threat to the fetus, it may be given transfusions inside the uterus every 10 days to two weeks until it has reached the 32nd to 34th weeks of pregnancy. Then a delivery should be done. These procedures must be done at a medical center that can care for high-risk pregnancies.

The baby should be delivered with as little trauma as possible. The placenta should not be removed manually to avoid squeezing cells from the baby's blood into the mother's blood stream. A newborn born with Rh disease should be seen immediately by a pediatrician who can do an exchange transfusion at once if necessary.

Prevention

Steps can be taken to assure that antibodies aren't made in the first place. This can be done by giving the mother a shot of anti-Rh antibodies within 72 hours of the delivery of the baby. This causes any of the baby's red blood cells that may have crossed into the mother's blood to be destroyed before sensitizing the mother's immune system.

This has to be done with each pregnancy -- normal or ectopic -- whether it ends in a delivery or an abortion.

If there is much blood loss during delivery, additional injections may be needed. Between 1 and 2% of the time this treatment fails. This is apparently because the mother has already become sensitized during pregnancy rather than at delivery.

The treatment can be done preventatively to mothers with Rh-negative blood and no apparent sensitization at about 28 weeks of pregnancy. Any antibodies circulating in the mother's blood are gradually destroyed and the mother remains unsensitized. The treatment should also be given after any bleeding or after amniocentesis or chorionic villus sampling.

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