Background: Aim was to estimate the prevalence of vitamin D deficiency in pregnant women and their infants and to analyse the effect of maternal vitamin D deficiency on the infant.Methods: A prospective study was done in the Department of Obstetrics and Neonatology in a tertiary centre in South India with 150 women seen in the antenatal clinic after 36 weeks of pregnancy were recruited. Serum vitamin D levels were obtained. Babies were followed up and sampled once between 10 and 20 weeks of age for vitamin D, calcium, phosphate and alkaline phosphatase. Vitamin D levels less than 20 ng/ml was considered as deficiency. Analysis of the data was done using SPSS 16.0 version.Results: Vitamin D deficiency was seen in 64.8% of the pregnant women. Follow up of 76 babies showed vitamin D deficiency in 72.6% infants. Significantly high levels of alkaline phosphatase were noted in infants who were born to mothers with vitamin D deficiency, which indicates risk of developing bone disease.Conclusions: This study highlights the high prevalence of Vitamin D deficiency in pregnant women and their infants in South India in a region with abundant sunshine. This study also emphasises treating vitamin D deficiency in pregnancy to reduce the risk of developing rickets in infancy.