Season, dietary factors, and physical activity modify 25-hydroxyvitamin D concentration during pregnancy

Purpose The objectives of this cross-sectional study were to define maternal and umbilical cord blood (UCB) 25-hydroxyvitamin D (25(OH)D) to characterize maternal factors modifying 25(OH)D during pregnancy and predict UCB 25(OH)D in two subgroups with Declined [Delta 25(OH)D < 0 nmol/l] and Increased [Delta 25(OH)D > 0 nmol/l] 25(OH)D concentration. Methods A complete dataset was available from 584 women. 25(OH)D was determined at gestational weeks 6-13 and in UCB. Baseline characteristics were collected retrospectively using questionnaires. Delta 25(OH)D was calculated as UCB 25(OH)D-early pregnancy 25(OH)D. Dietary patterns were generated with principal component analysis. Multivariate regression models were applied. Results Vitamin D deficiency was scarce, since only 1% had 25(OH)D concentration < 50 nmol/l both in early pregnancy and in UCB. Shared positive predictors of UCB 25(OH)D in the subgroups of Declined and Increased, were early pregnancy 25(OH)D (P < 0.001) and supplemental vitamin D intake (P < 0.04). For the Increased subgroup summer season at delivery (P = 0.001) and sandwich and dairy dietary pattern characterized with frequent consumption of vitamin D fortified margarine and milk products (P = 0.009) were positive predictors of UCB 25(OH)D. Physical activity (P = 0.041) and maternal education (P = 0.004) were additional positive predictors in the Declined group Conclusions Maternal and newborn vitamin D status was sufficient, thus public health policies in Finland have been successful. The key modifiable maternal determinants for 25(OH)D during pregnancy, and of the newborn, were supplemental vitamin D intake, frequent consumption of vitamin D fortified foods, and physical activity.