The Rh status describes whether or not the surface of your red blood
cells contains a special protein, called the Rh factor. If you have it,
you are Rh-positive, and if you don't, you are Rh-negative. About 85% of
the total population are Rh-positive, though it varies by race. For Blacks,
90-95% are postive and for Asians, it is 98-99% positive.
The Rh-factor only comes into play for pregnant women. If the mother
is Rh- and the father is Rh+, there is a chance that the child born could
be Rh+. Since the mother's blood isn't Rh+, the blood would react to the
baby's as if it were a foreign substance. This is not too dangerous during
a first pregnancy, as the immune system isn't that powerful against it.
However, with more pregnancies, the immune system grows stronger and the
mother's antibodies can cross the placenta and attach the fetus' red
blood cells. This is called Rh disease.
Rh disease used to cause problems ranging from severe jaundice and
the need for newborns to have blood transfusions, to preterm miscarriages
and stillbirths. Now, with new medicines, these effects are rarely ever
seen due to incompatible blood types.
Pregnant Rh- women are given shots of a medicine called RhoGAM (Rh
immune globulin) between the 28th and 29th weeks of pregnancy. After delivery,
if the child is Rh+, the mother is given a second shot 72 hours later. Rh-
women undergoing abortions are also given a shot prior or after the proceedure.
This is to prevent the mother's immune system from creating antibodies against
Rh+ blood to protect future pregnancies.
Sometimes RhoGAM is given in other situations in which fetal blood may
come in contact with the mother's, such as in the cases of chorionic villus
sampling (CVS), amniocentesis, an abortion or miscarriage, an ectopic pregnancy,
or vaginal bleeding.