What is Rh factor and why is it important?

Rhesus (Rh) factor is a protein some people have in their blood. If your blood has the protein, you are Rh positive. If your blood does not have the protein, you are Rh negative. About 85% of people are Rh positive. If you know your blood type, then you know if you are Rh negative or Rh positive. The + or - in your blood type tells you what your Rh type is. Your Rh type stays the same for your whole life.

If you have vaginal bleeding during pregnancy (like with an abortion, miscarriage, or during labor), fetal blood cells can enter your blood. If you are Rh negative, this can cause your body to develop Rh antibodies. These antibodies can cause serious problems in future pregnancies, which includes causing a severe anemia in the fetus.

Evidence shows that this risk is very low in pregnancies that are less than 10 weeks, even if you are Rh negative.

If you are Rh positive, you will not develop Rh antibodies.

Rhₒ(D) immune globulin (sometimes called RhoGAM) is a shot that can stop your body from producing Rh antibodies, so that you won’t have problems in future pregnancies. Some providers recommend this shot within 3 days of vaginal bleeding if you are Rh negative.

If you do not know your blood type, you can do a blood typing test at home or at a healthcare facility. If you choose to get further testing, please visit our Resources page to find a provider near you.

Your Hey Jane provider will discuss this further with you, too, in case you have any questions.