EVOLUTION OF BLOOD-COAGULATION ACTIVATORS AND INHIBITORS IN THE HEALTHY-HUMAN FETUS

Blood coagulation proteins were determined in 285 healthy fetuses from 19 to 38 weeks' gestation and compared with those of 60 normal full-t erm newborns and 40 adult controls. Prolongation of the coagulation sc reening tests, prothrombin time, activated partial prothrombin time, a nd thrombin clotting time, in fetuses throughout intrauterine life was explained by low levels of vitamin K-dependent factors (II, VII, IX, and X), contact factors (XI, XII, prekallikrein, and high-molecular-we ight kininogen), factor V, factor VIII, and fibrinogen, Low levels of antithrombin III, heparin cofactor II, protein C and protein S, and ti ssue factor pathway inhibitor were also found, and these probably cont ributed to a satisfactory hemostatic balance. Some of these parameters were evaluated by both immunologic and functional assays to detect po ssible ''fetal'' proteins. An increase in factor levels was observed a fter the thirty-fourth week of intrauterine life for most of the coagu lation activators and inhibitors, but only factors V and VIII reached adult values at birth. This study therefore showed that fetal hemostas is is a dynamic system that evolves gradually toward the neonatal stat e and then toward the adult state. (C) 1996 by The American Society of Hematology.