Vitamin K deficiency in breast-fed infants at one month of age.

PIVKA-II (protein induced by vitamin K absence or antagonist-II) was measured, as an indicator of vitamin K deficiency, in breast-fed infants of approximately 1 month of age. The infants consisted of three different groups: untreated (group 1); those given 5 mg vitamin K once at birth (group 2); and those given 5 mg twice, at birth and at 14 days after birth (group 3). At 1 month of age, the rate of PIVKA-II-positive infants and their PIVKA-II levels were significantly reduced in group 3 as compared with the levels of the other two groups, whereas these parameters were similar between groups 1 and 2. This observation suggested that vitamin K administration once at birth may be unsafe by 1 month of age. An additional administration of vitamin K seemed to be necessary for complete prevention of vitamin K deficiency, causing severe bleeding in breast-fed infants of approximately 1 month of age.