Determinants of maternal vitamin D concentrations in Slovenia: A prospective observational study

Summary Objective To analyze the vitamin D status of pregnant women in Slovenia and the factors influencing it. Methods The study was performed in Maribor University Medical Centre (location 46°N). Maternal serum 25-hydroxy-vitamin D (25(OH)D) in 4 groups of 100 pregnant women in 4 different seasons of the year was measured at the time of delivery. Data on life style, eating habits, sunbathing and intake of vitamin D supplements during pregnancy were obtained using a questionnaire. Information on maternal outcome was acquired from medical records. Duration of sunlight and average temperature in the month preceding delivery were calculated from meteorological data. Results The average maternal 25(OH)D concentration ranged from 28.5 ± 17.1 nmol/l in March to 54.8 ± 24.1 nmol/l in June ( p < 0.001). Severe vitamin D deficiency, i.e.