Oral Magnesium Supplementation for the Prevention of Preeclampsia: a Meta-analysis or Randomized Controlled Trials

Previous studies evaluating the role of magnesium supplementation as a preventative strategy for preeclampsia showed inconsistent results. We performed a meta-analysis or randomized controlled trials (RCTs) to evaluate the influence of oral magnesium supplementation on the incidence of preeclampsia in pregnant women. Relevant studies were obtained by search of Medline, Embase, and Cochrane's Library databases. A random effects model was used to pool the results. Influences of study characteristics of the outcome were evaluated by predefined subgroup analyses. Seven RCTs with 2653 pregnant women were included. Pooled results showed that oral magnesium supplementation during pregnancy significantly reduced the risk of preeclampsia (risk ratio [RR]: 0.76, 95% confidence interval [CI]: 0.59 to 0.98, P = 0.04) with no significant heterogeneity (P for Cochrane's Q test = 0.42, I2 = 1%). The result was not significant for the outcome of severe preeclampsia (RR: 0.54, 95% CI: 0.18 to 1.69, P = 0.29; I2 = 0%), although only two studies were available. Subgroup analysis showed that oral magnesium supplementation did not significantly reduce the risk of preeclampsia in normal pregnant women (RR: 0.91, 95% CI: 0.67 to 1.25, P = 0.57), but the preventative effect was significant in studies with normal and high-risk pregnant women (RR: 0.54, 95% CI: 0.35 to 0.83, P = 0.005; P for subgroup difference = 0.04). In conclusion, oral supplementation of magnesium may reduce the risk of preeclampsia, which may be more remarkable in high-risk pregnant women.