Perinatal consequences of maternal-fetal Rh blood group interaction in diabetic pregnancy: A nonimmunological perspective

Background: The recent discoveries about the structure of Rh protein that s uggest a transport function and the recent observations of a positive corre lation between Rh(D) protein and glycosylated hemoglobin levels in non-insu lin-dependent diabetes mellitus prompted us to review our data on diabetic pregnancy to evaluate the perinatal consequences of maternal-fetal Rh blood group interactions in a metabolic perspective. Subjects and Methods: One h undred thirty-two women with gestational diabetes and 120 women with preexi sting insulin-dependent diabetes mellitus were examined. Three hundred eigh ty-seven consecutive nondiabetic puerperae from the same population were co nsidered control subjects. Results: In both gestational and insulin-depende nt diabetes mellitus, an increased proportion of mother Rh(+)/newborn Rh(-) and a decreased proportion of mother Rh(-)/newborn Rh(+) joint phenotype h as been observed. No deviation has been observed for joint phenotypes in wh ich mother and newborn are similar [ie, Rh(+)/Rh(+) and Rh(-)/Rh(-)]. In th e situation of mother Rh(+)/newborn Rh(-), there is a relatively lower rate of fetal loss and a decreased tendency to high birth weight. On the contra ry, in pairs mother Rh(-)/newborn Rh(+) the fetus shows an increase of feta l loss and of tendency to high birth weight. Conclusions: The results are c ompatible with the hypothesis that when the density of Rh protein in the mo ther is higher than that in the fetus, the conceptus is relatively protecte d against the toxic effect of glucose. In the opposite genotypic combinatio n (ie, density of Rh protein higher in the fetus than in the mother), the f etus is relatively more susceptible to these effects.