[Levels of antithrombin III and proteins C in the newborn infant].

Antithrombin III and protein C levels were studied in cord blood from 91 babies born at term with weight adequate to their gestation age. No history of drug ingestion or any other cause of impaired blood coagulation in newborns was present in any of the mothers, and none of these had had thromboembolic diseases. Basic coagulation study and clinical status were normal in all the newborns. Antithrombin III was measured as antigen concentration and functional heparin cofactor, both values being similar (ratio: 0.97) and significantly lower than those of adults (p less than 0.001). Antigenic protein C was assayed by enzyme immunoassay, the value attained being also significantly lower than that of normal adults (p less than 0.001). Factor VII: C rates were assayed in order to establish the protein C/factor VII: C relationship, since this might be useful in detecting protein C deficiency due to the similar biological characteristics of both proteins. It was concluded that health normal newborns show decreased antithrombin III and protein C rates, probably due to lack of liver maturity.