Bleeding in newborn from vitamin K deficiency is still a major concern in Pediatrics. Intramuscular vitamin K prevents bleeding in newborn even those who are exclusively breast fed and thus at greatest risk for bleeding. Human milk vitamin K content is very low compared with standard infant formulas. Oral prophylactic vitamin K currently used in some countries, following the association found in a single report between childhood cancer and intramuscular vitamin K has produced controversial results. The role of vitamin K in preventing intraventricular hemorrhage in premature infants has not been sufficiently demonstrated.