The kinin-forming enzyme system in pregnancy and obstetrical DIC.

Levels of prekallikrein and HMW kininogen that had increased during pregnancy decreased with start of labor. The role of the kinin-forming system with oxytocin in the mechanism of labor was suggested from the results of decreased prekallikrein and HMW kininogen, appearance of a free kallikrein-like enzyme during labor, and from the case of arrested labor in which both prekallikrein and HMW kininogen were markedly decreased. Prekallikrein was markedly decreased in patients with acute obstetrical DIC and severe toxemia of pregnancy. The excessive activation of prekallikrein in DIC seemed to be of help for understanding such clinical signs as shock, abnormal labor, and increased permeability in obstetrical DIC.