It HAS BEEN assumed for many years that the premature infant suffered more from hemorrhagic disturbances than the full term infant and that the premature infant's blood was even more deficient in prothrombin. For this reason, it is customary for most physicians to administer some form of vitamin K to the premature infant as prophylaxis for hemorrhagic manifestations. Actually, the literature contains comparatively meager references to the behavior of prothrombin in the premature infant. Furthermore, in only a few instances are these reports founded on any series of any considerable size, and in numerous instances the results have been contradictory on many essential points.
The first observations on the prothrombin content of the blood of the premature infant were made by Hellman and Shettles1 in 1939. In 17 premature infants, these authors, using the two stage method of prothrombin determination, found that the prothrombin content of the blood of