Cost-effectiveness: Details on the number and frequency of interventions, outcomes and their associated morbidity will be collected. This material will form the basis for a subsequent cost-effectiveness study. Given that vitamin K is very inexpensive (oral vitamin K costs less than 5$ Canadian per dose in most jurisdictions) and the expense of bleeding is high (previous cost effectiveness studies have estimated that an episode of major bleeding costs more than 5000 $ Canadian per event (20)) it is very likely that the use of oral vitamin K will be highly cost-effective.