A lower dosage of calcium supplement than the level recommended by the World Health Organisation (WHO) is still effective in reducing the risk of pre-eclampsia and preterm birth.

A recent study conducted on pregnant women in Tanzania and India, comparing the efficacy of a low-dose calcium regimen equivalent to one 500-milligramme pill per day against the WHO recommended high-dose regimen equivalent to three 500-milligramme pills taken throughout each day, found that the low-dose was equally effective in preventing preeclampsia, a condition that can be life-threatening for both mothers and newborns.

The study published on January 11, in The New England Journal of Medicine, showed that the incidents of pre-eclampsia among women taking the low-dose calcium was comparable to those taking the high-dose calcium.

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The WHO currently recommends high-dose calcium supplement — equivalent to three calcium pills a day — for pregnant women who have low-calcium diets, predominantly low- and middle-income countries.

However, these findings from the study led by Harvard T.H. Chan School of Public Health and collaborators in Tanzania and India, challenge the WHO’s recommendation.

According to the authors of the study, the current WHO recommendation of three calcium pills per day may pose challenges for pregnant women, saying they could be costly for governments and health programmes. Lowering the dosage to one 500-milligramme pill per day could help overcome these barriers and reduce costs without compromising health benefits.

While calcium supplement is a known intervention in preventing pre-eclampsia and pre-term birth, the study is the first to evaluate the efficacy of a low-dose regimen versus a high-dose regimen.

“The current recommendation for pregnant women to take three calcium pills per day presents feasibility concerns for women and cost concerns for governments and public health programs,” said senior author Wafaie Fawzi, Richard Saltonstall Professor of Population Sciences and professor of nutrition, epidemiology, and global health in the study.

“As such, most middle and low-income countries have not implemented calcium supplementation in pregnancy, leaving women and infants unnecessarily vulnerable.”

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The researchers conducted two randomised, double-blind trials of 11,000 pregnant women in India and 11,000 pregnant women in Tanzania to assess if 500mg of calcium per day was as effective as 1,500mg of calcium per day in reducing the risks of pre-eclampsia and pre-term birth — defined as birth before 37 weeks of gestation.

Starting at less than 20 weeks of pregnancy, they received monthly supplies of daily calcium supplements, consisting of either three 500mg calcium pills or one 500mg calcium pill and two placebo pills. Their health was monitored during clinic visits each month of their pregnancy, at delivery and at six weeks postpartum.

The study found that low-dose calcium supplementation was as effective as high-dose calcium supplement in preventing the risk of preeclampsia. In the Tanzania trial, the incidence of preeclampsia was 3 percent among women taking 500mg of calcium per day and 2.7 percent among women taking 1,500mg of calcium per day.

The findings on preterm birth were mixed. In the India trial, the incident of pre-term birth was 11.4 percent among women taking 500mg of calcium per day and 12.8 percent women taking 1,500mg of calcium per day, indicating a similar effect of the two doses.