First Trimester Vitamin D, Vitamin D Binding Protein, and Subsequent Preeclampsia

Previous studies report an association between vitamin D deficiency and hypertension, including the pregnancy-specific disorder preeclampsia. Circulating vitamin D is almost entirely bound to vitamin D binding protein, which increases 2-fold during pregnancy and previous studies have not examined vitamin D binding protein or free vitamin D levels. We performed a nested case-control study within the Massachusetts General Hospital Obstetric Maternal Study, measuring first trimester total 25-hydroxyvitamin D (25[OH] D) and vitamin D binding protein and calculating free 25(OH) D levels. We compared these levels from pregnancies complicated by subsequent preeclampsia (cases, n=39) with those from normotensive pregnancies (controls, n=131). First trimester total 25(OH) D levels were similar in cases and controls (27.4 +/- 1.9 versus 28.8 +/- 0.80 ng/mL; P=0.435). Despite an association between higher first trimester blood pressures and subsequent preeclampsia, first trimester total 25(OH) D was not associated with first trimester systolic (r=0.11; P=0.16) or diastolic blood pressures (r=0.03; P=0.72). Although there was a trend toward increased risk of preeclampsia with 25(OH) D levels <15 ng/mL (odds ratio: 2.5 [95% CI: 0.89 to 6.90]), this was attenuated after adjustment for body mass index and other covariates (odds ratio: 1.35 [95% CI: 0.40 to 4.50]). First trimester vitamin D binding protein and free 25(OH) D levels were similar in cases and controls and were not associated with first trimester blood pressures. These data suggest that first trimester total and free 25(OH) D levels are not independently associated with first trimester blood pressure or subsequent preeclampsia. (Hypertension. 2010;56:758-763.)