Abbreviated “RhIG” (or “RhIg”), Rh immune globulin is a commercial biological substance used in the prevention of hemolytic disease of the fetus/newborn. RhIG is a concentrated form of an antibody against the main Rh antigen, “D.” It is given to D-negative mothers during pregnancy and in the first 72 hours after delivery of a D-positive baby, in order to prevent them from making anti-D. RhIG may help to clear any baby D-positive red blood cells from the mother’s circulation without inducing an immune response, but it may also directly suppress the maternal immune response. RhIG may also be used for prevention of anti-D formation in D-negative blood product recipients (though its use in that situation is much less defined). Finally, you will hear many people calling RhIG “RhoGAM,” but that is only one particular manufacturer’s version of RhIG. Not all RhIG is RhoGAM, so don’t say it unless that’s really what you mean (sorry, that’s a pet peeve!).