Calcium during pregnancy: when the best evidence compels us to change our approach

Hypertensive disorders of pregnancy remain among the leading causes of morbidity and mortality worldwide, with a disproportionate impact on low- and middle-income countries. In recent decades, calcium supplementation has been widely promoted as a simple and potentially effective intervention to prevent preeclampsia, supported by small clinical trials, Cochrane systematic reviews, and World Health Organization recommendations, which facilitated its incorporation into clinical guidelines and public policies. However, the 2025 update of the Cochrane review published in 2025 redefined this understanding. By restricting the analysis to trustworthy trials, requiring prospective registration, and exploring the impact of small-study effects, the novel review concludes that, in the global analysis, calcium supplementation may result in little or no difference in preeclampsia incidence (low certainty). Furthermore, when the analysis is restricted to large-scale trials with greater methodological robustness, there is high-certainty evidence of little or no difference in the incidence of preeclampsia or preterm birth. Consistent reductions were also not demonstrated in maternal mortality, severe maternal morbidity, or major adverse perinatal outcomes. This article critically reviews the trajectory of calcium as a preventive strategy, discusses the implications of the 2025 Cochrane review guidelines and clinical practice, and contrasts its role with low-dose aspirin, which is supported by more robust evidence.

Key words
Preeclampsia; Gestational hypertension; Calcium; Aspirin; Evidence-based medicine