A recent Cochrane systematic review has concluded that calcium supplementation during pregnancy does not significantly reduce the risk of pre-eclampsia or related adverse outcomes for mothers and infants. This comprehensive analysis involved over 37,000 pregnant women across ten randomized trials, challenging longstanding beliefs about the effectiveness of calcium in preventing hypertensive disorders during pregnancy.
Understanding Pre-Eclampsia and Calcium’s Role
Pre-eclampsia is a serious condition characterized by high blood pressure and can lead to severe complications for both mothers and their babies. It is linked to poor placental development and can have detrimental effects on the mother’s liver, kidneys, and brain. Traditionally, calcium supplementation has been viewed as a potential preventive measure, particularly for women with a history of pre-eclampsia.
Calcium is easy to obtain, relatively inexpensive, and generally safe for both mothers and their babies. Prior studies suggested that it might lower blood pressure among women previously affected by pre-eclampsia. Nevertheless, the latest findings indicate that these blood pressure-lowering effects do not translate into significant reductions in the incidence of pre-eclampsia.
Key Findings from the Systematic Review
The Cochrane review aimed to assess the impact of calcium supplementation on preventing pre-eclampsia and other hypertensive disorders during pregnancy. Researchers analyzed whether calcium could improve critical outcomes such as maternal and neonatal deaths, perinatal mortality, and the occurrence of preterm births.
To ensure the reliability of the review, researchers implemented stricter study-selection criteria than in previous analyses. Out of the initial studies considered, several were excluded due to concerns about data integrity, resulting in ten trials being included in the final analysis. Among these, eight compared calcium supplementation to a placebo, while two compared different dosages of calcium.
The review highlighted that, across the eight placebo-controlled trials, calcium supplementation showed minimal difference in the rates of pre-eclampsia. Focusing on larger studies with ≥500 participants, four trials that included 14,730 women provided high-certainty evidence, indicating that calcium supplementation does not significantly alter the risk of developing pre-eclampsia.
Additionally, there was no evidence supporting the notion that calcium supplementation reduces maternal deaths, severe complications due to pre-eclampsia, or perinatal mortality. The data also indicated no meaningful impact on the risk of preterm birth, with high-certainty evidence backing these conclusions among larger studies.
When comparing low-dose versus high-dose calcium supplementation, the review found no significant differences in pre-eclampsia risk. Given that maternal deaths are quite rare, it was challenging to draw conclusions based on dosage specifics. Evidence regarding neonatal death also remained uncertain, making it difficult to establish strong recommendations.
Importantly, most supplementation began mid-pregnancy, leaving unanswered questions about the potential effects of early calcium use. The review’s data did not sufficiently differentiate outcomes among women with low versus adequate dietary calcium intake or risk levels for pre-eclampsia, although subgroup analyses suggested no notable differences.
The authors concluded that the latest, most reliable evidence does not support calcium supplementation as an effective strategy for preventing pre-eclampsia or other hypertensive disorders during pregnancy. They stated, “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.”
This review, published in March 2025, reinforces the need for healthcare professionals to reconsider the role of calcium supplementation in prenatal care and encourages exploration of alternative methods for managing blood pressure during pregnancy.
