Longitudinal vitamin D status in pregnancy and the risk of pre-eclampsia

Please cite this paper as: Dr Wei SQ, Audibert F, Hidiroglou N, Sarafin K, Julien P, Wu Y, Luo ZC, Fraser WD. Longitudinal vitamin D status in pregnancy and the risk of pre-eclampsia. BJOG 2012;119:832839. Objective Whether vitamin D deficiency in pregnancy is a cause of pre-eclampsia remains controversial. Most previous studies to date have assessed exposure at only one time-point in pregnancy. We assessed longitudinal vitamin D status during pregnancy and the risk of pre-eclampsia. Design Prospective cohort study. Setting Seventeen urban obstetric hospitals, Canada. Population Pregnant women who were participants in a trial of vitamin C and E supplementation for the prevention of pre-eclampsia. Canadian participants who consented to participate in a biobank with plasma specimens available at the baseline visit were included (n = 697). Methods Maternal plasma 25-hydroxyvitamin D (25(OH)D) concentrations were measured at 1218 and 2426 weeks of gestation using chemiluminescence immunoassay. Main outcome measures Pre-eclampsia. Results Of the women, 39% were vitamin D deficient (25(OH)D <50 nmol/l). A strong positive correlation was observed in maternal 25(OH)D concentrations between the two gestational age windows (r = 0.69, P < 0.0001). Mean maternal 25(OH)D concentrations at 2426 weeks of gestation were significantly lower in women who subsequently developed pre-eclampsia compared with those who did not (mean +/- SD: 48.9 +/- 16.8 versus 57.0 +/- 19.1 nmol/l, P = 0.03). Women with 25(OH)D < 50 nmol/l at 2426 weeks gestation experienced an increased risk of pre-eclampsia (adjusted odds ratio 3.24, 95% confidence interval 1.377.69), whereas the association was not statistically significant for maternal 25(OH)D level at 1218 weeks of gestation. Conclusions Lower maternal 25(OH)D levels at late mid-trimester were associated with an increased risk of pre-eclampsia.