Term infants with clinical and laboratory findings of early onset sepsis who are >37 weeks of gestational age and will be admitted to Neonatal Care Unit of Kanuni Sultan Suleyman Training and Research Hospital will be included in this prospective study. The study group will consist of term neonates who are clinically suspected to have an early infection from the 1st day of life. Blood for neonatal and maternal vitamin D levels will be obtained from all infants and their mothers at the time of hospital admission. Only infants with high probable sepsis will consist the study group. The healthy infants who admit to our outpatient clinic for routine evaluation at postnatal day 3 with no signs of clinical and laboratory infection and are evaluated for hyperbilirubinemia will be referred to as the Control group. The Control group wll consist term infants with the same gestational and postnatal age of the infants that will be included in the study group. In both groups, maternal samples will be obtained at the postpartum period at the time of infant's hospitalization. Plasmas after separated and stored at -800C. Levels of 25-OHD were determined using Shimadzu LC-20AT model High Performance Liquid Chromatography (HPLC) system. Data will be analyzed using SPSS software and appropriate statistical analyses will be performed.