Low-dose calcium supplementation for preventing pre-eclampsia: a systematic review and commentary

Authors

  • GJ Hofmeyr,

    1. Effective Care Research Unit, East London Hospital Complex/University of the Witwatersrand/University of Fort Hare, East London, Eastern Cape, South Africa
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  • JM Belizán,

    1. Institute for Clinical Effectiveness and Health Policy (IECS), Buenos Aires, Argentina
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  • P von Dadelszen,

    Corresponding author
    1. Department of Obstetrics and Gynaecology and Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada
    • Correspondence: P von Dadelszen, Department of Obstetrics and Gynaecology and Child and Family Research Institute, University of British Columbia, Room V3-339, 950 West 28th Avenue, Vancouver, BC V5Z 4H4, Canada. Email pvd@cw.bc.ca

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  • and on behalf of the Calcium and Pre-eclampsia (CAP) Study Group

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    • Including Bergel E, Cormick G, Hall DR, Fawcus S, Lazaga Betran AP, Munjanja S, Novikova N, Oyebajo A, Purnat T, Roberts JM, Sawchuck D and Singata M.

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.

Objectives

To review the impact of lower dose calcium supplementation on pre-eclampsia risk.

Search strategy and selection criteria

We searched PubMed and the Cochrane Pregnancy and Childbirth Group trials register.

Data collection and analysis

Two authors extracted data from eligible randomised and quasi-randomised trials of low-dose calcium (LDC, <1 g/day), with or without other supplements.

Main 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.

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