The effect of formula versus breast feeding and exogenous vitamin K1 supplementation on circulating levels of vitamin K1 and vitamin K-dependent clotting factors in newborns

The influence of breast or formula feeding together with that of a single supplementation of vitamin K₁ at birth, on the vitamin K₁ level and vitamin K-dependent clotting factors were studied in 65 breast and 15 formula fed infants. All breast fed newborns without supplementation (n=25) had very low serum vitamin K₁ at weeks 1 and 6. Oral vitamin K supplementation (n=22) or i.m. (n=18) at birth resulted in high serum levels at week 1, while at week 6 the effect had disappeared. Formula fed infants had vitamin K₁ values within the normal adult range at all study points. The low serum levels of vitamin K₁ were not associated with haemorrhagic disorders or coagulation abnormalities. The mean values of vitamin K₁ in maternal sera at weeks 1 and 6 were 2.3 nmol/l and 1.8 nmol/l and in breast milk 2.7 nmol/l and 2.0 nmol/l respectively. No correlation existed between the values in breast milk and maternal serum. To maintain serum levels of vitamin K₁ within the adult physiological range, repeated administration of low doses is needed in breast fed newborns beyond 1 week of age.