Protein C levels in infancy and early childhood. Influence of breast feeding.

. Protein C antigen levels were measured in the plasma of healthy full term infants by electroimmunoassay. During the first three months of life (on day four, at one month, two months and three months of age) protein C antigen levels were compared in breast-fed and bottle-fed infants. None of the two groups of infants received vitamin K at birth. Only at the age of three months there was a significant difference between the groups. Unexpectedly infants, who were breast-fed, had a higher protein C level at three months of age. Levels were also measured in 15 healthy children between one and three years of age. The antigen levels increase with age to reach adult values at about three years of age.