title: Longitudinal vitamin D status in pregnancy and the risk of pre-eclampsia.
abstract: 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.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Seventeen urban obstetric hospitals, Canada.
  
  
  METHODS
  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 12-18 and 24-26 weeks of gestation using chemiluminescence immunoassay.
  
  
  METHODS
  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 24-26 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 24-26 weeks gestation experienced an increased risk of pre-eclampsia (adjusted odds ratio 3.24, 95% confidence interval 1.37-7.69), whereas the association was not statistically significant for maternal 25(OH)D level at 12-18 weeks of gestation.
  
  
  CONCLUSIONS
  Lower maternal 25(OH)D levels at late mid-trimester were associated with an increased risk of pre-eclampsia.
authors.affiliation: Department of Obstetrics and Gynecology, Sainte-Justine Hospital, University of Montreal, QC, Canada. shu.qin.wei@umontreal.ca
authors.forename: S Q
authors.initials: SQ
authors.lastname: Wei
authors.forename: F
authors.initials: F
authors.lastname: Audibert
authors.forename: N
authors.initials: N
authors.lastname: Hidiroglou
authors.forename: K
authors.initials: K
authors.lastname: Sarafin
authors.forename: P
authors.initials: P
authors.lastname: Julien
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: Z C
authors.initials: ZC
authors.lastname: Luo
authors.forename: W D
authors.initials: WD
authors.lastname: Fraser
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood / Q000172:deficiency*; D007118:Immunoassay; D016015:Logistic Models; D008137:Longitudinal Studies; D008163:Luminescent Measurements; D011225:Pre-Eclampsia / Q000097:blood / Q000209:etiology*; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
chemical_list: D015415:Biomarkers; D006887:Hydroxycholecalciferols