Factor VIII activity and factor VIII related antigen in newborns.

Factor VIII procoagulant activity and factor VIII related antigen were examined in 20 full-term and preterm newborn infants during the first days of life. The control group involved 15 adults volunteers. Factor VIII activity was estimated by a one-stage test and factor VIII related antigen was determined by immunelectrophoresis according to Laurell, using our own rabbit antiserum. The following results were obtained:--Factor VIII activity during the first 3 days of life did not differ from the normal range of the adult controls.--The concentration of factor VIII related antigen in newborns was markedly higher than in adults on the first, and to a lesser extent on the second, day of life.--The antigen concentration decreases on the second and following days of life to adult levels. The cause of this discrepancy cannot be completely explained but possible reasons are discussed.