A new Cochrane systematic review has found that calcium supplementation during pregnancy does not provide meaningful protection against pre-eclampsia or related complications for mothers and babies. The review analyzed data from 10 randomized controlled trials, including over 37,000 pregnant women.
Pre-eclampsia is a serious complication linked to high blood pressure in pregnancy, which can result in severe illness or death for both mother and child. Calcium supplements have previously been considered as a possible preventive measure, especially for those with a history of pre-eclampsia. However, this latest evidence challenges that assumption.
The updated review only included trials meeting strict trustworthiness standards, excluding several earlier studies due to concerns about data integrity. Eight studies compared calcium to placebo and two looked at different doses of calcium supplementation. Participants were drawn from a range of settings and had varying levels of dietary calcium intake.
The findings showed little difference in the incidence of pre-eclampsia between women who took calcium supplements and those who did not. High-certainty evidence from four large trials involving nearly 15,000 participants confirmed there was little to no reduction in pre-eclampsia risk with supplementation.
No convincing evidence was found that calcium reduces maternal deaths, severe complications from pre-eclampsia, or perinatal mortality. There was also no significant effect on the rate of preterm birth among supplement users compared to placebo groups. Evidence regarding adverse effects remains unclear due to limited reporting in the included studies.
Comparisons between low-dose and high-dose supplementation did not show any meaningful differences in outcomes. The rarity of maternal deaths made it difficult to draw conclusions about dose-specific effects on this outcome. Similarly, the impact on neonatal death remains uncertain.
Most study participants began taking supplements midway through pregnancy, so it is unknown whether starting earlier would make a difference. There was also insufficient data to determine if results varied according to baseline dietary calcium intake or individual risk for pre-eclampsia.
The authors concluded: “It is unlikely that further research would change the current evidence. Therefore, in future, research could focus on other ways to prevent blood pressure disorders during pregnancy.”
