Post-natal development of factor II (pre-prothrombin and prothrombin) in man.

Postnatal development of factor II molecule has been evaluated by three different methods in infants and children from 15 days to 7 years of age. The immunochemical determination of factor II showed that the plasma levels of this factor reached the lowest adult values between 4-7 months of age and rose slowly for all the first year; after this age the plasma concentration was steady. The adult range was reached from 15 to 120 days of age when the factor II was evaluated by the method of Owren and Aas (19) and by staphylocoagulase reagent.