One of the first tests a pregnant woman will have is a blood-type test. In addition to figuring out whether her blood type is A, B, AB or O, the test will determine her Rh factor.
Both men and women are either Rh-positive or Rh-negative, depending on whether there is a certain protein present on their red blood cells. An estimated 85 percent of the population is Rh-positive.
If an Rh-negative woman and an Rh-positive man have a child, there is a chance the baby will be Rh-positive. This 'Rh incompatibility' between the mother and fetus can cause potential problems when the mother's and baby's blood mix.
If the mother's immune system detects that the baby is Rh positive, then her body will produce antibodies against it. These antibodies can pose problems for future pregnancies.
To minimize the chance of any complications during the pregnancy, Rh-negative women receive an injection of Rh (D) immune globulin, commonly known as RhoGAM, at 24 - 28 weeks gestation and within 72 hours of delivery if the baby is Rh-positive. This vaccine prevents the mother's body from producing unwanted antibodies.
Rh-negative women who have had a miscarriage or have had trauma or bleeding during their first trimester will also have the RhoGAM as a precautionary measure.
Women who have already developed antibodies do not benefit from RhoGAM. They must be closely monitored by a health care professional to ensure their baby is healthy. Mothers who are sensitized can have babies with hemolytic disease. This can cause brain damage or even death in newborns.
"Determining Rh factor early on in pregnancy is another example of why good prenatal care is so important," added Graham.
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