If you are among the roughly 15% of the population that has a blood type negative for a protein called Rh factor, your doctor probably will recommend that you get a RhoGAM ® shot each time you give birth -- but you may also need the shot as part of treatment for miscarriage or other pregnancy loss.
Having Rh negative blood does not cause first-trimester miscarriages, and there's no evidence that being sensitized to Rh factor can contribute to first-trimester miscarriages -- but sensitization can increase the risk of complications later in pregnancy and might cause health problems in newborn babies born to Rh sensitized mothers. The availability of RhoGAM shots has greatly decreased the frequency of Rh sensitization in women, but if you are concerned (such as if you had a miscarriage in the past and did not get the shot), you can ask your doctor about testing for anti-Rh antibodies in order to confirm or rule out the condition. Women who are sensitized to Rh factor should be monitored very closely in future pregnancies (but the risk of sensitization after a miscarriage is very small).
Image © A.D.A.M.
Illustration of How Rh Incompatibility Affects an Unborn Baby