The neonatal period is probably the only time when a higher incidence of spontaneous thromboembolic complications may occur in the otherwise normal healthy individual, and this may be related to the activation of the coagulation system at the time of parturition. This study was performed to look at the newborn coagulation and anticoagulation systems and compare these with the changes in the maternal circulation in normal cases. Paired umbilical cord venous and maternal venous blood samples were obtained and plasma levels of protein C, protein S, antithrombin III, fibronopeptide A, fibrinogen, plasminogen, and fibrinolytic inhibitory activity were measured. The maternal plasma level was significantly higher in all cases except for fibrinopeptide A which was similar, and for fibrinolytic inhibitory activity which was lower (p < 0.05). A significant correlation exists between maternal and newborn protein C levels (p < 0.02) and fibrinolytic inhibitory activity (p < 0.05). The findings indicate that parturition leads to a similar degree of activation of the newborn coagulation system as shown by the fibrinopeptide A level. As their anticoagulants and fibrinolytic activity levels are lower and the fibrinolytic inhibitory activity is higher, the newborns are thus predisposed to thrombosis even in the absence of complications such as sepsis.