Background: Studies have suggested that vitamin D status at birth may be associated with a range of neonatal outcomes. Aim: The aim of this study was to assess the association between neonatal 25(OH)D3 concentration and gestational age, birth weight, ponderal index and size for gestational age. Method: Neonatal capillary blood stored as dried blood spots was used to asses 25(OH)D3 concentrations among 2814 subjects selected from a random population sub-sample of individuals, born in Denmark from May 1st 1981 to December 31st 2002. Results: There was an inverse association between 25(OH)D3 concentration and gestational age at birth (95%CI -1.5; -0.5, p < 0.001). There was an inverted U-shaped association between 25(OH)D3 and birth weight and ponderal index (p=0.04), but there was no association with size for gestational age. Conclusion: This study suggests that neonatal 25(OH)D3 concentration is associated with gestational age at birth, birth weight and ponderal index, but not with size for gestational age.