PROTEIN C LEVELS DURING THE FIRST MONTH OF LIFE

Protein C (PC) is a unique vitamin K dependent plasma protein which acts as an anticoagulant. Thromboembolism has been reported in kindreds with PC levels which are congenitally 38-60% of normal. PC was measured by electro-immunoassay in 47 neonates ranging in gestational age (GA) from 28-40 weeks. None had evidence of DIC; all had received vitamin K. On day 1 of life mean PC was 27% ± 2.9 SEM (range < 10 to 67%) of the normal adult mean. PC correlated with GA in the 22 infants who were healthy (r=.65 p<.01) but did not correlate in the 25 sick infants. Postnatally PC was 32% on day 7 and 31% on day 28. None of the infants had evidence of thromboembolism. Ca++ reduced the electrophoretic mobility of infants' PC indicating that it was γ carboxylated. It is concluded that 1) For at least the first 28 days of life, PC was below the range reported in kindreds with congenital deficiency and thromboembolism, yet thromboembolism did not occur in these neonates. 2) PC in the newborn is γ carboxylated indicating that the low levels are due to decreased synthesis and/or short half life. 3) PC levels in healthy newborns correlates with GA.