There is increasing evidence of an association between a low maternal vitamin D status and a high risk of adverse pregnancy outcomes. In a cross-sectional study, we investigated the vitamin D status of pregnant women to determine potentially influencing factors. Between December 2010 and February 2012, 261 maternal blood samples and 328 cord blood samples were collected for the analysis of 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone, alkaline phosphatase and Ca concentrations. Demographical characteristics and clinical data were recorded by a questionnaire and from medical files. The overall median maternal and cord blood 25(OH)D levels were 25·0 (interquartile range 12·6–45·5) nmol/l and 34·1 (interquartile range 17·7–58·6) nmol/l, respectively. During the winter months,98% of the maternal blood samples and 94% of the cord blood samples had 25(OH)D levels ,50 nmol/l. In the summer months, 49% of the women and 35% of the cord blood samples were vitamin D deficient. Using logistic regression models, significant risk factors for maternal vitamin D deficiency were found to be physical inactivity (adjusted OR (aOR) 2·67, 95% CI 1·06, 6·69, P=0·032) and a non-European country of origin (aOR 3·21, 95% CI 1·0, 10·28, P=0·047) after controlling for season and independent risk factors. These results are the first 25(OH)D data for pregnant women in Germany. They indicate the need for urgent implementation of strategies to prevent vitamin D deficiency by healthcare authorities that are in charge of preventing vitamin D deficiency, especially during these sensitive stages of life.