Magnesium supplementation in pregnancy.

Systematic review and meta-analysis of randomized trials in pregnant women with normal or high-risk pregnancies from Europe, America, Africa, and Asia. Across the active magnesium arms, 9,090 women and their babies were included in 10 trials, with participants recruited from early to late gestation and including both primigravidas and multiparous women.

Oral magnesium supplementation during pregnancy was evaluated across randomized trials using different magnesium salts, including magnesium oxide, citrate, gluconate, aspartate, aspartate-hydrochloride, hydrochloride aspartate, and stearate. Doses ranged from 365 mg/day to 4 g/day, started as early as before 18 weeks or later in pregnancy, and continued until delivery or hospitalization near term, with comparison to control or no supplementation.

Routine magnesium supplementation during pregnancy was not supported by the available evidence. Across randomized trials, magnesium did not significantly reduce perinatal mortality, small-for-gestational-age births, or pre-eclampsia, and maternal mortality was not reported. Some secondary outcomes suggested possible benefit, but findings were inconclusive and limited by study quality. The authors concluded that better-designed, adequately powered trials are still needed before magnesium can be recommended routinely in pregnancy.

The evidence base was limited by generally low study quality, inconsistent reporting, and heterogeneity in magnesium salt, dose, timing, and target population. Several outcomes were underpowered or not reported, including maternal mortality, which limits confidence in the overall conclusions.