Blood prothrombin, proconvertin and proaccelerin in normal infancy: questionable relationships to vitamin K

One hundred fourteen newborn infants were followed for the first 6 weeks of life by specific tests for concentrations of prothrombin, proconvertin and proaccelerin in the blood. The concentration of proaccelerin is usually above normal at birth, while those of the two other factors are below normal and fall further in the first 2 or 3 days as well as showing a secondary dip at some time in the second to the sixth week. These fluctuations are not significantly affected by small doses of vitamin K, given to mother before delivery or to infant at birth. This suggests an endogenous controlling mechanism. An experiment with a "synthetic plasma" suggests that the excess proaccelerin compensates for the deficiencies of the other two factors in preventing the normal infant from developing any bleeding condition.