Maternal serum type III procollagen peptide (P-III-P) and 7S domain of type IV collagen (7S) as indicators of placental damage caused by severe toxemia of pregnancy

Summary Using immunohistochemical techniques, we studied the localization of type III and IV collagen in normal and toxemic placentae at term. We measured the maternal serum levels of type III procollagen peptide, and type IV collagen 7S domain in nonpregnant women, normal term pregnant women, and cases with toxemia of pregnancy. The immunohistochemical studies revealed that type III collagen exists in the connective tissues of the villus core, and type IV collagen in the basement membrane of trophoblast cells and fetal vascular elements. Even in normal looking toxemic placentae, the amount of types III and IV collagen appeared to be increased compared with that in normal placentae. However, the amount of types III and IV collagen appeared to be decreased in the necrotic chorionic villi of severe toxemia. Measurement of the collagen-related substances showed that the levels in toxemic pregnancy, especially when severe were elevated compared with those in normal pregnancy. In toxemic pregnancy, the incidence of IUGR in the group with elevated P-III-P levels increased significantly, and increased further when both P-III-P and 7S levels were high. Our data support our hypothesis that P-III-P and 7S in maternal serum flow out from necrotized chorionic villi into the intervillus space, and that these measurements are significant indicators of placental damage caused by severe toxemia of pregnancy.