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Comment and Controversy

Low power limits findings in regard to magnesium

April 2007 · Vol. 19, No. 04
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There are no universal guidelines or protocols delineating when therapy should be commenced for preterm labor—or which treatment is preferred. However, the use of pharmacotherapy for tocolysis remains the mainstay of management of preterm labor, the most popular agents being magnesium sulfate, betamimetics, and calcium-channel blockers.

One goal of treatment is to delay birth for 48 hours so that corticosteroids can be administered to prevent respiratory complications or the mother can be transferred to a facility where an appropriate level of care can be delivered.

The Cochrane review of 23 trials involving 2,036 women did not find magnesium to be superior to control treatments.1 However, if that investigation is narrowed to include only studies focusing on the goal of preventing preterm birth within 48 hours, only 11 trials involving 881 women are relevant. Given that the test for heterogeneity chi-square=20.74, with a P value of .02, and I2=51.8%, a larger number of trials should be included to improve the power of the meta-analysis, and the individual trials themselves should have better power.

Therefore, it remains unclear whether magnesium effectively prevents preterm birth for 48 hours, compared with other agents. However, its lower side-effect profile may warrant its use in particular situations.

Brandon Daniels, MD, Ray Mercado, DO,
Theodore Hale, MD, and Jamie Le

Lincoln Medical and Mental Health Center
Bronx, NY


1. Crowther CA, Hiller JE, Doyle LW. Magnesium sulfate for preventing preterm birth in threatened preterm labour. Cochrane Database Syst Rev. 2002;(4):CD001060.-

With the right treatment, preterm birth can be averted
Cause of preterm labor may be psychological
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