[Histometric studies of placental villi in Rh incompatibility]

The delay in maturation of placental terminal villi in cases of Rh-incompatibility has often been described. The terminal villi of sixteen placentas from pregnancies complicated by Rh-incompatibility histometric were studied. Twenty-two placentas of healthy mothers who had born healthy babies after normal pregnancies served as a control group. The severity of the Rh-incompatibility was classified according to the clinical histories of the newborns and the criteria of Liley. The average area of a cross-section of a terminal villus was 3402 microns 2 (control group 2150 micronsoff; the degree of vascularization was calculated to be 6.5% (control group 30.5%). The other villous parameters measured or calculated show that maturation of the placenta is extremely retarded in cases of Rh-incompatibility. This failure in differentiation can not be compensated for by an enlargement of the organ as a whole. It was shown that the changes in the placental villi are closely correlated to the severity of the fetal disease.