Previous work from this laboratory has suggested there is a risk of hemorrhagic disease of the new-born (HDNB) in approximately one-third of term neonates, presumably as a result of vitamin K deficiency. Using the same assay for PIVKA (protein induced by vitamin K absence, prothrombin precursor), we studied 46 normal mother-infant pairs at term to investigate the relationship between neonatal and maternal PIVKA status. PIVKA was found in 13 infants (28%) and in seven mothers (15%). Maternal PIVKA status correlated with infant status (p < 0.03). These data suggest that fetal vitamin K deficiency and risk of HDNB may be a consequence of maternal deficiency of the vitamin.