Protein C activity and antigen in premature and fullterm newborn infants.

Blood was obtained from 23 premature infants (birthweights 950-2910 g at 26-35 gestational weeks), and 27 fullterm infants (birthweights 2930-4900 g at 37-42 gestational weeks). Protein C concentration and activity were analysed. In preterm infants, protein C concentrations were 2.9-24% of adult values, and those of protein C activity 6-32%, the corresponding figures for term infants being 16-60% and 8.5-60%. Protein C concentrations were below 10% of adult values in four low birthweight infants, three of whom had significant haemorrhages. Protein C activity was below 10% of adult values in three infants, all of whom suffered from major haemorrhages.