Rh Disease in Pregnancy

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Rh antigen is found on red blood cells and forms early in fetal life. However, 15% of white Americans and 5% of black Americans do not have this antigen on their blood cells. The antigen is a dominant genetic trait, that means that if one of the two genes that produce the antigen is positive and the other is negative, that individual will have the Rh antigen present on the red blood cells and that person will be Rh positive. If Rh positive blood is mixed with Rh negative blood, antibodies will form that will destroy blood cells that have the Rh antigen present. This does not happen when Rh positive and Rh positive blood are mixed, nor when Rh negative and Rh negative are mixed.

If an Rh negative woman and an Rh positive man are pregnant, the possibility of a baby that has Rh positive blood is 60%. If there is a mixing of a small amount of the baby's blood into the mother, it could cause Mom to make antibodies against the baby's blood. This is called Rh iso-immunization. If this occurs, the antibodies can be detected by a blood test. These antibodies can cross the placenta and destroy the baby's red blood cells.

RhoGam, an Rh immunoglobulin, prevents the mother from forming antibodies. RhoGam cannot be used if the mother already has antibodies.
     An antibody test is done at 28 weeks on an Rh negative Mom and if the test is negative, she is given an injection of RhoGam. She will also have been given RhoGam is she has had a CVS or amniocentesis. Mom will also receive RhoGam within seventy-two hours of delivery if the baby is Rh positive.
    An Rh negative mother that has antibodies against Rh positive blood can pass the antibodies to the baby through the placenta. The antibodies can then attack the baby's red blood cells which carry the Rh antigen.
    An Rh isoimmunized pregnancy requires extremely close observation. The baby can have extreme difficulties including hemolytic anemia, which is anemia caused by the destruction of red blood cells, and intra-uterine death.

PRE-PREGNANCY: Your antibody titer, the amount of antibody you have, should be assessed as a baseline before your get pregnant. You may have up to a 60-70% chance of having an Rh positive baby if your partner is Rh positive. Your past obstetric history and the amount of problems your babies had are important. A current pregnancy will be as complicated or more complicated.

TREATMENT IN PREGNANCY/PRENATAL CARE: Your antibody titer will be assessed frequently by blood tests if you have Rh iso-immunization. Once your titer reaches a critical level, you should have amniocentesis done to assess the severity of the baby's problem. The fluid is tested for bilirubin, a substance made when red blood cells are broken down. If and when the baby is found to be in danger and severely anemic, he may be transfused while still in-utero. This is done using ultra-sound guidance and transfusing the red blood cells into the baby's umbilical cord. Percutaneous Umbilical Cord Sampling (PUBS) or Cordocentesis, transfusing directly into the umbilical cord, has been used since 1983. The baby will be followed closely, and if imminent danger is found should be delivered, even prematurely. Babies can be delivered as soon as their lungs are mature.
Babies are exchange transfused after birth. This means that their blood is removed and fresh, healthy blood replaces it. The improved outcome for Rh babies can be attributed to the improved techniques in transfusing the babies in-utero.

ADDITIONAL RESOURCES THAT MAY HELP:

	Rh Disease and Pregnancy
	Questions about Rh Disease
	Rh Incompatibility
	Thrive about Rh Disease
	Links to More Information

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Excerpts from: The Family Pregnancy © 1995: MJ Bovo, The Family Pregnancy, Second Edition, currently in production, and Do You Have Any Questions? © 1995: MJ Bovo, are contained within this page. Reprints are not permitted under any circumstances. Please see Terms of Use for full expanation. Violations of the Copyright Code are taken seriously and appropriate action IS TAKEN AGAINST VIOLATERS.