The Blood Coagulation and Fibrinolytic Systems in the Newborn and the Mother at Birth

Summary The coagulation and fibrinolytic systems were investigated in the mother and in the cord blood of the infant at term immediately after delivery and striking differences in both these systems were found. Low levels of factors II (prothrombin), VII, IX and X contrasted with the increased level of factors II, VII and X and a normal level of factor IX in the mother. Increased levels of factors V and VIII were found in the newborn and highly significant correlation was present between the maternal and neonatal levels. The levels of fibrinogen and plasminogen in the baby were half those found in the maternal blood. A high level of fibrinolytic activity was found in all the newborn infants in contrast to the diminished activity present in the maternal blood. The cord blood had a very high level of inhibitor to urokinase‐ induced lysis. The increased fibrinolytic activity in the infant may have a protective role for the rapid clearance of intravascular fibrin. High levels of circulating inhibitor in the baby would serve to protect the susceptible plasma proteins and confine the results of plasminogen activation to the digestion of fibrin. The findings suggest that normal delivery activates the clotting and fibrinolytic systems of the baby and the mother, probably due to thromboplastin entering the fetal and maternal circulations during placental separation.