The epithelial and capillary basal laminae of the placenta in maternal diabetes mellitus.

The thickness of the epithelial and endothelial basal laminae was determined in placentas from mothers without known metabolic disease (control) and mothers with diabetes mellitus. The measurements were carried out on electron micrographs. Frequency distributions and statistical parameters were calculated; in 20 cases, 16,331 values were measured. In all cases, the epithelial and endothelial basal laminae were thickest in edematous and fibrotic villi. They were thinner in placentas from diabetic mothers than in controls. Particularly thin basal laminae were found in regions with syncytiovascular membrances. The thinner basal laminae found in the placentas of diabetic mothers are considered to be the result of compensatory growth processes with formation of ontogenetically younger villous parts. The thicker basal laminae in fibrotic and edematous villi may result from a swelling of the basal laminae or possibly from an increased synthesis or a decreased decomposition of the basal laminae. The finding of very thin basal laminae in the region of the so-called syncytiovascular membranes may be of importance for the placental exchange function.