Background and aims Besides its well known role in bone metabolism, vitamin D also has immune modulatory effects. Although the link between vitamin D deficiency and various infections has been reported, no study has evaluated the effect of vitamin D levels on neonatal sepsis. The aim of this study was to evaluate the effect of vitamin D levels on early-onset sepsis (EOS) in term infants. The association between the severity of vitamin D deficiency and EOS was also investigated.

Methods Fifty term infants with clinical and laboratory findings of EOS (Study group) and 50 healthy infants with no signs of clinical and laboratory infection (Control group) were enrolled. Infants with high probable sepsis consisted the Study group and the healthy infants with no signs of clinical and laboratory infection were referred to as the Control group. Blood for neonatal and maternal vitamin D levels were obtained from all infants and their mothers at the postpartum period at the time of hospital admission.

Results Both maternal and neonatal 25-hydroxyvitamin D (25-OHD) levels in the Study group were significantly lower compared with those of the Control group (p < 0.001). A positive correlation was detected between maternal and neonatal 25-OHD levels. Both maternal and neonatal 25-OHD levels were significantly higher in summer and with regular vitamin D supplementation during pregnancy. Severe vitamin D deficiency was significantly more common in the sepsis group.

Conclusions EOS in term infants is associated with significantly lower maternal and neonatal 25-OHD levels. We also found that levels of 25-OHD in neonates were positively correlated with those in mothers. These data suggest that adequate vitamin D supplementation during pregnancy may be helpful to prevent EOS in term neonates.