Vitamin D and hypertension in pregnancy

Abstract

Purpose: Vitamin D Deficiency is common, particularly in northern latitudes. We examined the association between vitamin D status and hypertension in late pregnancy. Methods: A case-control study was conducted during two time periods: September-October, 2008, and January-March, 2009, in women near term. A case was defined as having two or more documented blood pressure readings above 140/90 (either/or) at any time during pregnancy (n=78). Controls had at least two blood pressure readings, with none above 140/90 during pregnancy (n=109). Serum 25-hydroxyvitamin D (25(OH)D) was measured in all participants. Results: In the summer, 13% of controls and 29% of the cases had 25(OH) D levels < 50 nmol/L. During the winter, these numbers rose to 44% and 49% respectively. Both cases and controls were more likely to be vitamin D deficient in the winter (p=0.002). There was a negative correlation between BMI and 25(OH)D (r=-0.202, p=0.002). In univariate analysis, cases had lower 25(OH)D (p=0.046), but also higher body mass index, so that in multivariate analysis 25(OH)D status was no longer significant. There was no difference in mean oral daily vitamin D intake (dietary intake and supplements, 746 and 785 IU respectively). Controls gained less weight in pregnancy. There was a negative correlation between the highest blood pressure measured in pregnancy and 25(OH)D levels (r= -0.118; p=0.012). Conclusion: There is a high prevalence of vitamin D deficiency in pregnant women recruited in Saskatoon, Saskatchewan. Women with low circulating vitamin D concentrations are more likely to have hypertension.