Vitamin D deficiency during pregnancy is associated with negative health consequences for mothers and their infants. Data on the vitamin D status of pregnant women in Switzerland are scarce. A three-centre study was conducted in the obstetric departments of Zurich, Bellinzona and Samedan (Switzerland) to investigate the prevalence and determinants of vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D)<50 nmol/l) in 3rd-trimester pregnant women living in Switzerland (n 305), and the correlation between 25(OH)D in pregnant women and their offspring at birth (n 278). Demographic and questionnaire data were used to explore the determinants of vitamin D deficiency. Median concentration of serum 25(OH)D in the third trimester of pregnancy was 46·0 nmol/l (1st–3rd quartiles: 30·5–68·5), representing a 53·4 % prevalence of vitamin D deficiency. 25(OH)D levels in the umbilcal cord blood (median: 50·0 nmol/l; 1st–3rd quartiles: 31·0–76·6) strongly correlated with mothers’ serum 25(OH)D (Spearman’s correlation ρ=0·79, P<0·001). Multivariable logistic regression analysis showed that significant determinants of vitamin D deficiency in pregnant women were centre of study, country of origin, season of delivery and vitamin D supplement intake. Near-term BMI, skin colour, use of sunscreen and mothers’ education, although each not individually significant, collectively improved the ability of the model to explain vitamin D status. Low vitamin D levels were common in this sample of pregnant women and their newborns’ cord blood. Vitamin D supplement intake was the most actionable determinant of vitamin D status, suggesting that vitamin D supplementation during pregnancy should receive more attention in clinical practice.

Hypovitaminosis D is common in Asian Indians. Physicians often prescribe 1500 μg (60 000 IU) cholecalciferol per week for 8 weeks for vitamin D deficiency in India. Its efficacy to increase serum 25-hydroxy vitamin D (25(OH)D) over short (2 months) and long (1 year) term is not known. We supplemented a group of twenty-eight apparently healthy Asian Indians detected to have low serum 25(OH)D (mean 13·5 (sd 3·0) nmol/l) on screening during January–March 2005. Serum parathyroid hormone (PTH) level was supranormal in 30 % of them. Oral supplementation included 1500 μg cholecalciferol per week and 1g elemental Ca daily for 8 weeks. Serum 25(OH)D, total Ca, inorganic P and intact (i) PTH were reassessed in twenty-three subjects (twelve females and eleven males) who had follow up at both 8 weeks and 1 year. At 8 weeks the mean 25(OH)D levels increased to 82·4 (sd 20·7) nmol/l and serum PTH normalized in all. Twenty-two of the twenty-three subjects had 25(OH)D levels>49·9 nmol/l. At 1 year, though the mean 25(OH)D level of 24·7 (sd 10·9) nmol/l was significantly higher than the baseline, all subjects were 25(OH)D deficient. Five subjects with supranormal iPTH at baseline showed recurrence of biochemical hyperparathyroidism. Thus, with 8 weeks of cholecalciferol supplementation in Asian Indians with chronic hypovitaminosis D, mean serum 25(OH)D levels would be normalized and serum PTH value would be reduced to half. However, such quick supplementation would not maintain their 25(OH)D levels in the sufficient range for 1 year. For sustained improvement in 25(OH)D levels vitamin D supplementation has to be ongoing after the initial cholecalciferol loading.