Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems (Cochrane Review)

A substantive amendment to this systematic review was last made on 15 October 2001. Cochrane reviews are regularly checked and updated if necessary.

Background: Calcium supplementation may prevent high blood pressure through a number of mechanisms and may help to prevent preterm labour.

Objectives: The objective of this review was to assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child adverse outcomes.

Search strategy: We searched the Cochrane Pregnancy and Childbirth Group trials register (October 2001) and the Cochrane Controlled Trials Register (Issue 3, 2001) and we contacted study authors.

Selection criteria: Randomised trials comparing at least one gram daily of calcium during pregnancy with placebo.

Data collection and analysis: Eligibility and trial quality were assessed. Data extraction was carried out and double entered.

Main results: Eleven studies were included, all of good quality. There was a modest reduction in high blood pressure with calcium supplementation (relative risk 0.58, 95% confidence interval 0.43 to 0.79). The effect was greatest for women at high risk of hypertension (relative risk 0.47, 95% confidence interval 0.22 to 0.97) and those with low baseline dietary calcium (relative risk 0.38, 95% confidence interval 0.22 to 0.64). There was also a modest reduction in the risk of pre-eclampsia with calcium supplementation (relative risk 0.35, 95% confidence interval 0.20 to 0.60). The effect was greatest for women at high risk of hypertension (relative risk 0.22, 95% confidence interval 0.12 to 0.42) and those with low baseline calcium intake (relative risk 0.29, 95% confidence interval 0.16 to 0.54). There was no overall effect on the risk of preterm delivery, although there was a reduction in risk amongst women at high risk of hypertension (relative risk 0.45, 95% confidence interval 0.24 to 0.83). There was no evidence of any effect of calcium supplementation on stillbirth or death before discharge from hospital. There were fewer babies with birthweight < 2500g (RR 0.45, 95% CI 0.22 to 0.95). In one study, childhood systolic blood pressure > 95th percentile was reduced (RR 0.59, 95% CI 0.39 to 0.91).

Reviewers' conclusions: Calcium supplementation appears to be beneficial for women at high risk of gestational hypertension and in communities with low dietary calcium intake. Optimum dosage requires further investigation.

Citation: Hofmeyr GJ, Atallah AN, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems (Cochrane Review). In: The Cochrane Library, Issue 3, 2003. Oxford: Update Software.

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This is an abstract of a regularly updated, systematic review prepared and maintained by the Cochrane Collaboration. The full text of the review is available in The Cochrane Library (ISSN 1464-780X).

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