Background: Preterm infants (PTs) have a higher risk for vitamin D deficiency, which is associated with a higher incidence of co -morbidities & mortality. Vitamin D deficiency plays a role in sepsis because vitamin-D-related pathways are associated with various immunological and endocrine functions and also Vitamin D is an important for immune system development.
Aim: To demonstrate the association between vitamin D level and occurrence of late onset sepsis (LOS) in PTs.
Methods: This is a case-control study included preterm babies who were admitted to Minia University Hospital's Neonatal Intensive Care Unit (NICU). Study groups were included; Group I of 65 PTs≤30-32 weeks of gestational age (GA) and/or≤1500g birth at 28 days of age and this group of preterm babies were subdivided into two subgroups at follow up at one month of age into Group Ia with low vitamin D Baseline < 20 ng/ml, Group Ib with vitamin D Baseline > 20 ng/ml on follow up at one month of life. While group II include 50 full term babies >32weeks of gestational age (GA) and/or>1500g birth at 28 days of age healthy ones served as control.
Results: The PTs with vitamin D deficiency showed a higher incidence of LOS and correlation was observed between incidence of LONS(r: - 0.16 p: 0.0001), length of hospital stay  (r: 0-.77; p:0.001) with vitamin D levels in neonates especially preterm ones .
Conclusion: Preterm neonates with low vitamin D levels are more likely to develop sepsis with more disease severity, higher mortality, and higher duration of hospital admission also, a percentage of critically ill neonates have vitamin D deficiency.