ABSTRACT
Awomannotimmunizedbythefirstsuchpregnancyisatapproximatelythesameriskin asecondD+,ABO-compatiblepregnancy.However,asparityincreasesandthenumberof womencapableofanRhimmuneresponsediminishesbecausetheyhavebecomeimmunized, thenumberwhomountaprimaryimmuneresponsewilldecreasebecauseofagreaterresidual numberof"nonresponders."BythetimeanRh-womanhascompletedherfifthABO-compatible,Rh+pregnancy,thereisabouta50%probabilitythatshewillbeRhimmunized. BeforetheRhpreventionera,0.8-1.0%ofpregnantwomeninManitobawereRhimmunized. About25-30%ofD-womenarenonresponders.TheydonotbecomeRhimmunizeddespite manyD+pregnancies,althoughsomemaybecomeRhimmunizedfollowingexposuretoa large(massive)amountofD+blood.
