A comprehensive review of calcium supplementation during pregnancy has determined it does not prevent pre-eclampsia or related adverse outcomes. The Cochrane systematic review analyzed data from 10 randomised trials involving over 37,000 pregnant women, revealing that calcium supplements provide little to no reduction in the incidence of this serious condition.
Pre-eclampsia is a significant health concern, linked to high blood pressure during pregnancy. It poses risks for both mothers and infants, potentially leading to severe complications. Despite previous assumptions that calcium could be beneficial, recent findings challenge this notion, particularly for women with a history of pre-eclampsia.
Calcium Supplementation: A Previously Considered Preventive Measure
Calcium has long been viewed as an accessible and safe option for pregnant women. It is inexpensive and widely available, leading to its recommendation as a preventive strategy against hypertensive disorders. Earlier studies indicated that calcium might help lower blood pressure, especially in women previously affected by pre-eclampsia. However, whether these effects translate into meaningful prevention has remained uncertain.
The updated Cochrane review, which utilized stricter study-selection criteria, provides more robust evidence than previous analyses. This review aims to clarify whether calcium supplementation effectively reduces the risk of pre-eclampsia and its associated complications.
Rigorous Study Analysis and Findings
The review included only randomized controlled trials that met rigorous trustworthiness standards, leading to the exclusion of several earlier studies due to data integrity issues. Ultimately, the review incorporated ten eligible studies, with 37,504 participants. Among these, eight trials compared calcium with a placebo, while two focused on contrasting low-dose (500 mg/day) versus high-dose (1,500 mg/day) elemental calcium.
The analysis of placebo-controlled studies indicated minimal difference in pre-eclampsia incidence. Focusing on larger trials involving 14,730 women, the evidence showed that calcium supplementation is associated with little to no difference in pre-eclampsia risk compared to placebo.
Moreover, the research found no convincing evidence that calcium supplementation reduces maternal death, severe complications of pre-eclampsia, or perinatal mortality. The data suggested that calcium did not significantly impact the risk of preterm birth, which was backed by high-certainty evidence in the larger study subgroup.
The review also looked at whether dosage differences affected outcomes. It concluded that varying calcium doses did not lead to meaningful changes in pre-eclampsia risk. Due to the rarity of maternal death, no specific conclusions could be drawn regarding dose-related effects, and evidence surrounding neonatal death remained uncertain.
Researchers noted that most supplementation began mid-pregnancy, preventing them from assessing the potential effects of early calcium use. Additionally, data limitations hindered the ability to differentiate effects based on dietary calcium intake or the risk of pre-eclampsia among participants.
In summary, the authors of the study concluded that current evidence does not support calcium supplementation as an effective prevention method for pre-eclampsia or other hypertensive disorders during pregnancy. They stated, “It is unlikely that further research would change the current evidence. Therefore, future research could focus on other ways to prevent blood pressure disorders during pregnancy.”
The findings were published in the Cochrane Database of Systematic Reviews by researchers C. A. Cluver, C. Rohwer, and A. C. Rohwer on March 15, 2024.
