Coagulation and fibrinolytic factors in the first week of life in healthy infants.

Coagulation and fibrinolytic factors were determined daily in 74 healthy term and preterm infants to obtain a reference standard. A gestational age dependency was determined for antithrombin III, factor II, and plasminogen. The mean concentrations of antithrombin III and factor II in preterm infants increased to term values within the first week of life. Factor X levels declined independent of vitamin K administration. The values for the fibrinolytic system (alpha 2-antiplasmin and plasminogen) remained stable.