title: Low-dose calcium supplementation for preventing pre-eclampsia: a systematic review and commentary.
abstract: BACKGROUND
  Epidemiological data link low dietary calcium with pre-eclampsia. Current recommendations are for 1.5-2 g/day calcium supplementation for low-intake pregnant women, based on randomised controlled trials of ≥1 g/day calcium supplementation from 20 weeks of gestation. This is problematic logistically in low-resource settings; excessive calcium may be harmful; and 20 weeks may be too late to alter outcomes.
  
  
  OBJECTIVE
  To review the impact of lower dose calcium supplementation on pre-eclampsia risk.
  
  
  METHODS
  We searched PubMed and the Cochrane Pregnancy and Childbirth Group trials register.
  
  
  METHODS
  Two authors extracted data from eligible randomised and quasi-randomised trials of low-dose calcium (LDC, <1 g/day), with or without other supplements.
  
  
  RESULTS
  Pre-eclampsia was reduced consistently with LDC with or without co-supplements (nine trials, 2234 women, relative risk [RR] 0.38; 95% confidence interval [95% CI] 0.28-0.52), as well as for subgroups: LDC alone (four trials, 980 women, RR 0.36; 95% CI 0.23-0.57]); LDC plus linoleic acid (two trials, 134 women, RR 0.23; 95% CI 0.09-0.60); LDC plus vitamin D (two trials, 1060 women, RR 0.49; 0.31-0.78) and a trend for LDC plus antioxidants (one trial, 60 women, RR 0.24; 95% CI 0.06-1.01). Overall results were consistent with the single quality trial of LDC alone (171 women, RR 0.30; 95% CI 0.06-1.38). LDC plus antioxidants commencing at 8-12 weeks tended to reduce miscarriage (one trial, 60 women, RR 0.06; 95% CI 0.00-1.04).
  
  
  CONCLUSIONS
  These limited data are consistent with LDC reducing the risk of pre-eclampsia; confirming this in sufficiently powered randomised controlled trials would have implications for current guidelines and their global implementation.
authors.affiliation: Effective Care Research Unit, East London Hospital Complex/University of the Witwatersrand/University of Fort Hare, East London, Eastern Cape, South Africa.
authors.forename: G J
authors.initials: GJ
authors.lastname: Hofmeyr
authors.forename: J M
authors.initials: JM
authors.lastname: Belizán
authors.forename: P
authors.initials: P
authors.lastname: von Dadelszen
mesh_terms: D002136:Calcium, Dietary / Q000008:administration & dosage* / Q000009:adverse effects; D019587:Dietary Supplements / Q000009:adverse effects; D005260:Female; D006801:Humans; D006973:Hypertension / Q000517:prevention & control*; D011225:Pre-Eclampsia / Q000517:prevention & control*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000517:prevention & control*; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome
chemical_list: D002136:Calcium, Dietary
keywords: Calcium replacement; calcium supplement; eclampsia; low-dose calcium; pre-eclampsia