Effectiveness of Calcium Supplementation for Improved Outcomes in Hypertensive Pregnancies in Developing Countries: A Systematic Review and Meta-Analysis

Background: Hypertensive disorders of pregnancy are common and result in a substantial health burden. Evidence from epidemiological studies have shown an inverse relationship between calcium intake and development of hypertension in pregnancy. This study evaluated the evidence of effectiveness of calcium supplementation for improved outcomes in hypertensive pregnancies in developing countries. Method: A systematic review was undertaken. Medline, Scopus, Hinari, and Cochrane databases were searched for literature published between 1985 to October 2020. Only RCTs published in English were included. Primary outcomes were pre-eclampsia, eclampsia and gestational hypertension. Secondary outcomes were preterm birth and low birth weight. Data were extracted from 21 selected RCTs for analysis. Meta-analysis was performed where data were available from more than one study for an outcome. Log risk ratio and the 95% confidence interval were estimated for each study. Risk ratios were directly pooled across studies using fixed-effects model if heterogeneity was absent, otherwise a random-effects model was used. P<0.05 was considered statistically significant, except for the test of heterogeneity where P<0.10 was used. Results: Pooled analysis showed that calcium supplementation significantly reduced the risk of pre-eclampsia and gestational hypertension by 49% [RR: 0.51, (95% CI: 0.38, 0.67), P<0.001] and 53% [RR: 0.47, (95% CI: 0.32, 0.69), P<0.001] respectively when compared with placebo. The best intervention for lowering risk of pre-eclampsia and gestational hypertension was calcium supplement plus other co-supplements. The incidence of preterm delivery was lowered by 48% [RR: 0.52, (95% CI: 0.35, 0.78), P=0.001] in the intervention group. Conclusion: There is strong evidence that maternal calcium supplementation is associated with improved outcomes in hypertensive pregnancies in developing countries.