Magnesium supplementation in pregnancy

Abstract

Background: Many women, especially those from disadvantaged backgrounds, have intakes of magnesium below recommended levels. Magnesium supplementation during pregnancy may be able to reduce fetal growth retardation and pre-eclampsia, and increase birthweight.

Objectives: The objective of this review was to assess the effects of magnesium supplementation during pregnancy on maternal, neonatal and paediatric outcomes.

Search strategy: We searched the Cochrane Pregnancy and Childbirth Group trials register.

Selection criteria: Randomised and quasi-randomised trials of dietary magnesium supplementation during pregnancy.

Data collection and analysis: Suitability for inclusion and methodological quality were separately assessed by each reviewer. Data were independently extracted by two reviewers.

Main results: Six trials involving 2637 women were included. Only one of these trials was judged to be of high quality. Compared with placebo, oral magnesium treatment from before the 25th week of gestation was associated with a lower incidence of preterm birth (odds ratio 0.71, 95% confidence interval 0.52 to 0.95). There was also less maternal hospitalisation during pregnancy, fewer cases of antepartum haemorrhage, a lower incidence of low birthweight and small for gestational age infants. Poor quality trials are likely to have resulted in a bias favouring magnesium supplementation.

Reviewer's conclusions: There is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.