Calcium supplementation (reduction of risk of preeclampsia)

• dietary supplementation with at least 1 g of calcium a day reduces the relative risk of pre-eclampsia - however there is no clear effect on the risk of stillbirth or the baby dying before discharge from hospital (9 trials, 6763 babies; relative risk 1.04, 95% confidence interval 0.65 to 1.66)
• calcium supplementation effects seemed strongest for high risk women and those with low dietary calcium
  • data from the World Health Organization trial of women with low calcium intake support a modest reduction in the risk of pre-eclampsia associated with calcium supplementation rather than placebo (171/4151 v 186/4161; relative risk 0.91, 0.69 to 1.19)
    • relative reductions in risk also seen were:
      • severe gestational hypertension (relative risk 0.71, 0.61 to 0.82)
      • eclampsia (0.68, 0.48 to 0.97)
      • delivery before 32 weeks (0.82, 0.71 to 0.93)

A meta-analysis of 14 trials involving 2459 women was undertaken (2). This evaluated the effect of calcium supplementation during pregnancy on blood pressure and preeclampsia. The pooled analysis of all studies revealed a reduction in systolic BP of -5.40 mmHg and in diastolic BP of -3.44 mmHg. There was a reduction in the incidence of hypertension and preeclampsia in women who had undertaken calcium supplementation.

A systematic review concluded that calcium supplementation during pregnancy reduces the risk of pre-eclampsia by about half (3)

• the greatest benefit occurs in women at high risk and those with low dietary calcium intake

Reference:

• (1) BMJ. 2006 Feb 25;332(7539):463-8.
• (2) Villar J et al. World Health Organization randomized trial of calcium supplementation among low calcium intake pregnant women. Am J Obstet Gynecol. 2006 Mar;194(3):639-49
• (3) Hofmeyr GJ et al. Dietary calcium supplementation for prevention of pre-eclampsia and related problems: a systematic review and commentary. BJOG. 2007 Aug;114(8):933-43