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Observations indicate that the first born RhO (D)-positive (Rh+) infant of an RhO. (D)-negative (Rh-) mother may have a higher risk of hemolytic disease if the grandmother is Rh+ rather than Rh-. This “grandmother theory” gives rise to the speculation that the primary sensitizing dose of Rh+ blood was received in-utero by the Rh- baby from the Rh+ mother. To investigate the incidence and the timing of a possible maternal-fetal transfusion and its resultant antibody stimulation in the Rh- infant born of an Rh+ mother, 402 infant serums (292 at birth and 110 at 2 days) were studied for presence of anti-D antibody (modified Lalezari method) and retested in 237 patients at 1-6 months of age. In addition, 275 blood samples from 2 day old infants were tested for presence of maternal Rh+ red cells (fluorescein labeled anti-globulin technic). Although several reactions initially appeared to identify antibody, none of these proved to be anti-D when these serums were tested with a 10 red-cell panel. Maternal Rh+ red cells were detected in 3 neonatal blood samples (1.1%), but no anti-D antibody was found in these 3 babies on follow-up-at 1, 3 and 6 months in 2 babies or at birth and 4 months in the other. Published reports indicating a significant risk for parturition sensitization of the Rh- neonate of the Rh+ mother cannot be corroborated by our studies.(Support:Ortho Diagnostics)

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