Magnesium supplementation in pregnancy

Makrides M, Crowther CA

Published Online:

February 17, 2010

There is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.

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 birth weight. The objective of this review was to assess the effects of magnesium supplementation during pregnancy on maternal, neonatal and paediatric outcomes. The reviewers concluded that there is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.

Abstract (click to read)

Background:

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's Trials Register (June 2001). We updated this search on 1 October 2009 and added the results to the awaiting classification section.

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 the two reviewers.

Main results:

Seven trials involving 2689 women were included. Six of these trials randomly allocated women to either an oral magnesium supplement or a control group, whist the largest trial with 985 women had a cluster design where randomisation was according to study centre. The analysis was conducted with and without the cluster trial.

In the analysis of all trials, oral magnesium treatment from before the 25th week of gestation was associated with a lower frequency of preterm birth, (relative risk (RR) 0.73, 95% confidence interval (CI) 0.57 to 0.94), a lower frequency of low birth weight (RR 0.67, 95% CI 0.46 to 0.96) and fewer small for gestational age infants (RR 0.70, 95% CI 0.53 to 0.93) compared with placebo. In addition, magnesium treated women had less hospitalisations during pregnancy (RR 0.66, 95% CI 0.49 to 0.89) and fewer cases of antepartum haemorrhage (RR 0.38, 95% CI 0.16 to 0.90) than placebo treated women.

In the analysis excluding the cluster randomised trial, the effects of magnesium treatment on the frequencies of preterm birth, low birth weight and small for gestational age were not different from placebo.

Of the seven trials included in the review, only one was judged to be of high quality. Poor quality trials are likely to have resulted in a bias favouring magnesium supplementation.

Authors' conclusions:

There is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.

[Note: The 15 citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

This record should be cited as:

Makrides M, Crowther CA. Magnesium supplementation in pregnancy. Cochrane Database of Systematic Reviews 2001, Issue 4. Art. No.: CD000937. DOI: 10.1002/14651858.CD000937

Assessed as up to date:

July 24, 2001

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Primary Review Group:

Pregnancy and Childbirth Group

Health topics:

Pregnancy & childbirth > Nutrition during pregnancy and postpartum > Vitamins/minerals

Pregnancy & childbirth > Preterm labour > Prediction/prevention

Complementary & alternative medicine > Pregnancy & childbirth > Nutrition during pregnancy and postpartum

Complementary & alternative medicine > Pregnancy & childbirth > Preterm labour

Cochrane Summaries^beta

Independent high-quality evidence for health care decision making

Magnesium supplementation in pregnancy

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