Magnesium maintenance therapy for preventing preterm birth after threatened preterm labour

  • Review
  • Intervention

Authors

  • Shanshan Han,

    1. The University of Adelaide, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, Adelaide, South Australia, Australia
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  • Caroline A Crowther,

    Corresponding author
    1. The University of Adelaide, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, Adelaide, South Australia, Australia
    • Caroline A Crowther, ARCH: Australian Research Centre for Health of Women and Babies, Discipline of Obstetrics and Gynaecology, The University of Adelaide, Women's and Children's Hospital, 72 King William Road, Adelaide, South Australia, 5006, Australia. caroline.crowther@adelaide.edu.au.

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  • Vivienne Moore

    1. University of Adelaide, Department of Public Health, Adelaide, South Australia, Australia
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Abstract

Background

Magnesium maintenance therapy is one of the types of tocolytic therapy used after an episode of threatened preterm labour (usually treated with an initial dose of tocolytic therapy) in an attempt to prevent the onset of further preterm contractions.

Objectives

To assess whether magnesium maintenance therapy is effective in preventing preterm birth after the initial threatened preterm labour is arrested.

Search methods

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2010).

Selection criteria

Randomised controlled trials of magnesium therapy given to women after threatened preterm labour.

Data collection and analysis

The review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. We checked data entry.

Main results

We included four trials, which recruited 422 women. Three trials had high risk of bias and none included any long-term follow up of infants. No differences in the incidence of preterm birth or perinatal mortality were seen when magnesium maintenance therapy was compared with placebo or no treatment; or alternative therapies (ritodrine or terbutaline). The risk ratio (RR) for preterm birth (less than 37 weeks) for magnesium compared with placebo or no treatment was 1.05, 95% confidence interval (CI) 0.80 to 1.40 (two trials, 99 women); and 0.99, 95% CI 0.57 to 1.72 (2 trials, 100 women) for magnesium compared with alternative therapies. The RR for perinatal mortality for magnesium compared with placebo or no treatment was 5.00, 95% CI 0.25 to 99.16 (one trial, 50 infants) and also compared with alternative treatments, was 5.00, 95% CI 0.25 to 99.16 (one trial, 50 infants). Women taking magnesium preparations were less likely to report palpitations or tachycardia than women receiving alternative therapies (RR 0.26, 95% CI 0.13 to 0.52, three trials, 237 women) but were much more likely to experience diarrhoea (RR 7.66, 95% CI 2.18 to 26.98, three trials, 237 women).

Authors' conclusions

There is not enough evidence to show any difference between magnesium maintenance therapy compared with either placebo or no treatment, or alternative therapies (ritodrine or terbutaline) in preventing preterm birth after an episode of threatened preterm labour.

Plain language summary

Giving oral magnesium maintenance therapy to women to prevent preterm birth after stopping threatened preterm labour

Magnesium does not reduce preterm birth or improve the outcome for the infant when given to women after contractions of preterm labour have been stopped.

Babies born preterm, before 37 weeks, may not survive or they may have later physical health and developmental problems if they do survive. Women whose preterm labor is stopped with tocolytic therapy remain at high risk of preterm birth. A variety of agents (tocolytics) are used to halt the uterine contractions. These include betamimetics, calcium channel blockers, magnesium sulfate, and oxytocin receptor antagonists. Subsequent tocolytic maintenance medication has been advocated. Oral magnesium has been used to prevent further early contractions. We identified four randomised controlled trials involving a total of 422 women for this review. The trials did not demonstrate any differences between magnesium maintenance therapy and placebo or other treatments (ritodrine or terbutaline) in the prevention of preterm birth or perinatal deaths. The trials were too small to exclude either important benefits or harms from magnesium maintenance therapy. Magnesium was less likely than the alternative tocolytics (betamimetics) to result in side effects, particularly palpitations or tachycardia, although diarrhoea was more likely. This finding is based on very few studies, and none of them looked at the infants' later development.

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