Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems

  • Review
  • Intervention


  • GJ Hofmeyr,

  • AN Atallah,

  • L Duley

Prof G Justus Hofmeyr, Director/Hon. Professor, Effective Care Research Unit, University of the Witwatersrand, University of Fort Hare, Eastern Cape Department of Health, Frere and Cecilia Makiwane Hospitals, Private Bag X 9047, East London, Eastern Cape, 5200, SOUTH AFRICA.



High blood pressure during pregnancy is a common cause of serious morbidity and death. Calcium supplementation may reduce the risk of high blood pressure through a number of mechanisms and may help to prevent preterm labour.


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 (September 2003) and the Cochrane Central Register of Controlled Trials (Issue 3, 2003). 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 reduction in the incidence of high blood pressure with calcium supplementation (10 trials, 6634 women: relative risk (RR) random effects model 0.58, 95% confidence intervals (CI) 0.43 to 0.79). The effect was greater amongst women at high risk of developing hypertension (four trials, 327 women: RR 0.47, 95% CI 0.22 to 0.97), and those with low baseline dietary calcium (five trials, 1582 women: RR 0.38, 95% CI 0.22 to 0.64).

There was also a reduction in the risk of pre-eclampsia with calcium supplementation (11 trials, 6894 women: RR 0.35, 95% CI 0.20 to 0.60). The effect was greatest in women at high risk of hypertension (five trials, 587 women: RR 0.22, 95% CI 0.12 to 0.42), and those with low baseline calcium intake (six trials, 1842 women: RR 0.29, 95% CI 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 developing hypertension (four trials, 568 women: RR 0.45, 95% CI 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, < 2500 g in women at high risk of hypertension (two trials, 449 women: RR 0.45, 95% CI 0.22 to 0.95).

In one study, childhood systolic blood pressure > 95th percentile was reduced (514 women: RR 0.59, 95% CI 0.39 to 0.91).

Authors' conclusions

Calcium supplementation appears to reduce the risk of high blood pressure in pregnancy, particularly for women at high risk of gestational hypertension and in communities with low-dietary calcium intake. Optimum dosage and the effect on more substantive outcomes requires further investigation.

Plain language summary

Plain language summary

Calcium supplements may prevent high blood pressure and help prevent preterm labour

High blood pressure is a major cause of death in pregnant women and newborn babies worldwide. Preterm birth (birth before 37 weeks) is often caused by high blood pressure and is the leading cause of newborn deaths, particularly in low-income countries. The review of trials found that calcium supplementation during pregnancy is a safe and relatively cheap means of reducing the risk of high blood pressure in women at increased risk, and women from communities with low dietary calcium. No adverse effects have been found but further research is needed into the ideal dosage for supplementation and to confirm the above results, which are influenced by several rather small trials.