Vitamin K and Thrombotest values in full term infants.

The vitamin K dependent clotting factors were measured by the 'Thrombotest' on the second day of life in 72 healthy full term babies, half of whom had received vitamin K at birth. Forty eight of these were breast fed, and those not given vitamin K had significantly lower Thrombotest values than those who had received vitamin K. By contrast, administration of vitamin K did not affect the Thrombotest values in bottle fed babies, the values in treated and untreated babies being the same and of the same order as the level in those breast fed babies treated with vitamin K. Serial study of 18 normal breast fed babies tested at day 0 and day 2 showed a pronounced drop in the Thrombotest values in this period, which was prevented by one intramuscular dose of 1 mg vitamin K at birth. Although none of the neonates in this study showed haemorrhagic disease, nine of the 24 untreated breast fed infants had Thrombotest values below 10% on day 2, at which level bleeding has been reported.