Objective:Vitamin D deficiency is a serious health problem despite a general improvement in socio-economic status in Turkey. The aim of this study was to evaluate maternal vitamin D status and its effect on neonatal vitamin D concentrations after a support programme for pregnant women was introduced. A second aim was to identify risk factors for vitamin D deficiency in a district of İstanbul.Methods:A total of 97 pregnant women and 90 infants were included in this study, conducted between January and October 2016. The demographic data, risk factors and daily vitamin intake were recorded. Serum levels of vitamin D, calcium, phosphorus and alkaline phosphatase in all subjects were measured. The mothers and newborns were divided into groups based on their vitamin D levels. The relationship between vitamin D levels and risk factors was analyzed.Results:Mean ± standard deviation vitamin D levels for the women and their infants were found to be 14.82±11.45 and 13.16±7.16 ng/mL, respectively. The number of mothers and infants was significantly higher in the deficient group, and their mean vitamin D levels significantly lower (9.02±1.34 and 8.80±1.06 ng/mL, respectively) (p<0.001, p<0.001). Only 14.4% of pregnant women took 1000-1200 IU/day of vitamin D. When the mother groups were evaluated in terms of risk factors, there were significant differences in daily vitamin intake and clothing style (p<0.001 and p<0.001 respectively).Conclusion:Vitamin D deficiency in pregnant women and their infants is still a serious health problem in Turkey, although a vitamin D support programme during pregnancy has been launched by the department of health.