Maternal Vitamin D Deficiency Increases the Risk of Preeclampsia

We aimed to assess the effect of maternal 25-hydroxyvitamin D [25(OH)D] concentration on the risk of preeclampsia and to assess the vitamin D status of newborns of preeclamptic mothers. DESIGN AND SETTING: We conducted a nested case-control study of pregnant women followed from less than 16 wk gestation to delivery (1997-2001) at prenatal clinics and private practices. PATIENTS: Patients included nulliparous pregnant women with singleton pregnancies who developed preeclampsia (n = 55) or did not develop preeclampsia (n = 219). Women's banked sera were newly measured for 25(OH)D. MAIN OUTCOME MEASURE: The main outcome measure was preeclampsia (new-onset gestational hypertension and proteinuria for the first time after 20 wk gestation). Our hypotheses were formulated before data collection.

Adjusted serum 25(OH)D concentrations in early pregnancy were lower in women who subsequently developed preeclampsia compared with controls [geometric mean, 45.4 nmol/liter, and 95% confidence interval (CI), 38.6-53.4 nmol/liter, vs. 53.1 and 47.1-59.9 nmol/liter; P