OXYGEN DIFFUSIVE CONDUCTANCE IN PLACENTAE FROM CONTROL AND DIABETIC WOMEN

Random tissue sections of placentae from control and diabetic deliveri es were analysed stereologically. The aim was to test whether or not a daptations in oxygen diffusive conductances occur to help compensate f or fetal hypoxic stress in utero. Organs were from 34 control and 55 d iabetic deliveries (39 from White's classes A, B, C and 16 from classe s D, F/R) arranged in two major groups (ABC and DFR). Tissue samples w ere fixed in formalin and processed for wax histology. Stereological a nd physicochemical quantities were used to calculate the partial condu ctances of six tissue layers, viz. maternal erythrocytes and plasma, v illous trophoblast, villous stroma, fetal plasma and fetal erythrocyte s. From partial conductances and birthweights, total and specific cond uctances for each placenta were determined. No differences were detect ed between diabetic placentae in different classes (A, B, C, D, F/R). However, both the ABC and DFR groups of diabetic placentae had higher total diffusive conductances than control organs. The increase was in the order of 7-25 % and persisted even when adjustments were made for apparent differences in birthweights. The principal contributors to th ese changes were the post-trophoblastic (fetally located) tissue layer s. These findings suggest that the diabetic placenta adapts to facilit ate the diffusion of oxygen across the placenta and, thereby, to assis t the hypoxic fetus.