Low-dose calcium as effective as higher dose in preventing preeclampsia, preterm birth

Key takeaways:

• Preeclampsia incidence was similar in trials for calcium 500 mg and 1,500 mg.
• Researchers found mixed results in preterm birth incidence between two different studies.

Low-dose calcium supplementation of 500 mg daily may be as effective as the current WHO recommendation for high-dose supplementation of 1,500 mg daily in reducing preeclampsia and preterm birth risks, researchers reported.

“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,” Wafaie W. Fawzi, MD, BS, DrPH, Richard Saltonstall professor of population sciences and professor of nutrition, epidemiology and global health at the Harvard T.H. Chan School of Public Health, said in a related press release. “As such, most middle- and low-income countries have not implemented calcium supplementation in pregnancy, leaving women and infants unnecessarily vulnerable.”

Fawzi, Christopher Sudfeld, ScD, associate professor of global health and nutrition at the Harvard T.H. Chan School of Public Health, and colleagues conducted two randomized, double-blind trials with data from 11,000 pregnant women in India in one trial and 11,000 pregnant women in Tanzania in the other to evaluate whether calcium supplementation of 500 mg daily was as effective as 1,500 mg daily to reduce preeclampsia and preterm birth risks. All participants were pregnant for the first time and received monthly supplies of daily calcium supplements with three 500 mg pills or one 500 mg pill plus two placebo pills beginning at less than 20 weeks gestation.

Researchers monitored each participant’s health during monthly clinic visits during pregnancy, at delivery and at 6 weeks postpartum.

The two primary outcomes for each trial were preeclampsia and preterm birth.

Results were published in The New England Journal of Medicine.

In the India trial, cumulative preeclampsia incidence was 3% in the 500 mg group and 3.6% in the 1,500 mg group (RR = 0.84; 95% CI, 0.68-1.03). In the Tanzania trial, the cumulative preeclampsia incidence was 3% in the 500 mg group and 2.7% in the 1,500 mg group (RR = 1.1; 95% CI, 0.88-1.36). These findings were consistent with the 1.54 noninferiority margin for preeclampsia.

The percentage of live preterm births was 11.4% in the 500 mg group and 12.8% in the 1,500 mg group in the India trial (RR = 0.89; 95% CI, 0.8-0.98). These findings were within the 1.16 noninferiority margin.

In the Tanzania trial, the percentage of live preterm births was 10.4% in the 500 mg group and 9.7% in the 1,500 mg group (RR = 1.07; 95% CI, 0.95-1.21), which exceeded the noninferiority margin. The preterm birth risk observed in the Tanzania trial was slightly less than predicted, researchers noted, and therefore the confidence intervals were wider than expected.

“Overall, our findings show that a single pill per day can be as effective as three,” Sudfeld said. “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. https://www.eurekalert.org/news-releases/1030562?. Published Jan. 10, 2024. Accessed Jan. 10, 2024.