Abstract: Objective To investigate the risk factors of early-onset sepsis (EOS) in neonates and its relationship with vitamin D levels. 
Methods A total of 56 neonates with EOS admitted to the Second Affiliated Hospital of Hebei North University were selected as the EOS group, and another 60 neonates born in the same period excluding infections were selected as the control group. The clinical data of neonates and corresponding mothers in the two groups were collected, and the levels of 25-hydroxyvitamin D ［25-(OH)D］ in venous blood of neonates and mothers in the two groups were detected. The clinical data and vitamin D levels in the two groups were analyzed. 
Results The incidences of maternal chorioamnionitis, premature rupture of membranes≥18 h, placental abruption, meconium-stained amniotic fluid, fetal distress and asphyxia at birth in EOS group were higher than those in the control group (P＜0.05). The levels of 25-(OH)D of mothers and neonates in EOS group were significantly lower than those in the control group (P＜0.01). Multivariate Logistic regression analysis showed that maternal chorioamnionitis, premature rupture of membranes≥18 h and neonatal asphyxia at birth were risk factors for EOS (P＜0.05). Neonatal 25-(OH)D level was a protective factor for EOS (P＜0.05). The area under the receiver operating characteristic curve (AUC) of neonatal 25-(OH)D level for the prediction of EOS was 0.833 (P=0.013), and the Jordan index was 0.512. The cut-off value of neonatal 25-(OH)D level was 21.29 nmol/L, and the sensitivity and specificity for the prediction of EOS were 83.3% and 67.9% respectively. The levels of 25-(OH)D in mothers and neonates were positively correlated in both EOS group and control group (P＜0.05). 
Conclusion Maternal chorioamnionitis, premature rupture of membranes≥18 h and neonatal asphyxia at birth are risk factors for EOS, while neonatal 25-(OH)D level is a protective factor for EOS and also a good predictive index. Pregnant women should pay attention to vitamin D supplementation to reduce the incidence rate of EOS. Early identification of risk factors and detection of vitamin D levels is helpful for comprehensively assessing the risk of EOS. 

Key words: neonatal sepsis, vitamin D, influencing factor analysis