Seasonal variations of vitamin D concentrations in pregnant women and neonates in Slovenia.

Objective: While foreign research shows a high prevalence of vitamin D deficiency in pregnant women and consequently in neonates, we do not have any data on vitamin D concentration in these risk groups for Slovenia. We performed a prospective study to evaluate vitamin D concentration in pregnant women and neonates in Maribor region.
Study Design: We determined 25-hydroxy-vitamin D concentration from blood samples taken before delivery from 100 pregnant women who gave birth in Maribor University Clinical Centre in September and December 2013, respectively, and from the cord blood of their neonates. We collected data on nutrition and sun exposure during pregnancy. We calculated the vitamin D concentrations in pregnant women and neonates according to season of birth and use of nutrition supplements, determined the vitamin D levels in some pregnancy complications and checked the correlation of maternal and neonatal vitamin D concentrations.
Results: The average vitamin D concentration in the September group was 54.3±25.2nmol/L, and in the December group 33.3±18.6nmol/L (p<0.001). Optimal vitamin D concentration (>80nmol/L) was reached by 12.0% of pregnant women in September and by only 2.0% in December. Women who took nutrition supplements containing vitamin D during pregnancy had significantly higher vitamin D levels than those who did not (September 68.9±27.0nmol/L vs. 46.5±20.3nmol/L, p<0.001; December 38.7±17.9nmol/L vs. 30.2±18.4nmol/L, p=0.028). Neonates had higher average levels of vitamin D than their mothers but there was a good correlation between maternal and neonatal vitamin D values.
Conclusion: Vitamin D deficiency is very common in pregnant women in Slovenia as well, especially in winter and in those women who do not take nutrition supplements containing vitamin D.
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