Rh Factor Blood Test - Overview & Result

Rhesus (Rh) factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you’re Rh positive. If your blood lacks the protein, you’re Rh negative. The test is also called red blood cell (RBC) antibody screen.

Rh positive is the most common blood type. Having an Rh negative blood type is not an illness and usually does not affect your health. However, it can affect your pregnancy. Your pregnancy needs special care if you’re Rh negative and your baby’s father is Rh positive.

 The Rh factor test is done during pregnancy to identify a woman’s Rh factor.  If the mother shows a Rh negative result, the baby’s father might need an Rh factor test, too.
Rh Positive
There’s nothing to worry about.
Rh Negative
If the mother is Rh negative and the baby is Rh positive, the mother’s body might produce proteins called Rh antibodies after exposure to the baby’s red blood cells. The antibodies produced aren’t a problem for this pregnancy, but it causes great concern with the next pregnancy.
In next pregnancy, if the baby is Rh positive again, mother’s body will produce Rh antibodies, the antibodies can cross the placenta and damage the baby’s red blood cells, leading to anemia, which could be life-threatening.
Prevention: in the first pregnancy,  during the first trimester and again during week 28 of pregnancy, the mother has to take a blood test to screen antibodies.
If the mother hasn’t started to produce Rh antibodies, she will be given an injection of a blood product called Rh immune globulin is . The immune globulin prevents the body from producing Rh antibodies during pregnancy.
When the baby is delivered –
  • Rh negative, no additional treatment is needed.
  • Rh positive, the mom will receive a second injection.
If the antibody screen shows that the mom is already producing antibodies, an injection of Rh immune globulin won’t help. The baby will be carefully monitored. If necessary, he or she might be given a blood transfusion through the umbilical cord during pregnancy or immediately after delivery.
The below chart shows the possible scenarios when a mom, or a dad is Rh negative.
Mother’s Rh factor Father’s Rh factor Baby’s Rh factor Precautions
Rh positive Rh positive Rh positive None
Rh negative Rh negative Rh negative None
Rh positive Rh negative Could be Rh positive or Rh negative None
Rh negative Rh positive Could be Rh positive or Rh negative Rh immune globulin injections
* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.