Preeclampsia and preterm birth risk may be reduced by calcium dose lower than current WHO standard

According to two trials of 11,000 pregnant women in India and in Tanzania, low-dose calcium supplementation (500 milligrams per day) appears as effective at reducing the risk of preeclampsia and preterm birth as high-dose calcium supplementation (1,500 milligrams per day). The study was published in The New England Journal of Medicine.

The World Health Organization currently recommends high-dose calcium supplementation—equivalent to three calcium pills a day—for pregnant women in contexts with low-calcium diets, predominantly low- and middle-income countries. Lowering the pill burden to one 500mg calcium pill per day would reduce adherence barriers for women and reduce costs for governments and health programs without sacrificing health benefits.

While calcium supplementation is a known intervention to help prevent preeclampsia and preterm birth—it is estimated to halve a pregnant woman’s risk of developing preeclampsia and reduce an infant’s risk of being born preterm by 25%—the study is the first to evaluate the efficacy of a low-dose regimen versus a high-dose regimen. The findings provide an opportunity to revise the WHO’s current recommendation that women with low-calcium diets—most women who live in low- and middle-income countries—receive high-dose calcium supplementation throughout pregnancy.

The study found that low-dose calcium supplementation was as effective as high-dose calcium supplementation in preventing the risk of preeclampsia. In the India trial, the incidence of preeclampsia was 3.0% among women taking 500mg of calcium per day and 3.6% among women taking 1,500mg of calcium per day. In the Tanzania trial, the incidence of preeclampsia was 3.0% and 2.7%, respectively.

“Overall, our findings show that a single pill per day can be as effective as three,” said joint first author Christopher Sudfeld, associate professor of global health and nutrition. “With a reduced pill burden for women and lower costs for governments and programs that buy calcium pills, calcium supplementation should be considered widely implementable in the places it’s needed most—and should start saving thousands of maternal and newborn lives.”

Reference: Preeclampsia and preterm birth risk may be reduced by calcium dose lower than current WHO standard; New England Journal of Medicine; DOI: 10.1056/NEJMoa2307212