Giving magnesium sulphate to stop women from going into premature labour could reduce the chances of babies later being diagnosed with moderate to severe cerebral palsy, said researchers in the US.

The multicenter, placebo-controlled, double-blind trial was the work of Dr Dwight Rouse, from the University of Alabama at Birmingham, and colleagues, and is published in the 28 August online issue of the New England Journal of Medicine, NEJM.

For the research, Rouse and colleagues studied 2,241 women who were at risk of going into premature labour between their 24th and 31st week of pregnancy. The women were randomly assigned to receive either magnesium sulphate, given intravenously as a 6g bolus followed by a constant infusion of 2g per hour, or a matching placebo.

Magnesium sulphate is used to slow down the contractions of the uterus and thereby delay labour.

The researchers followed the surviving babies for two years. They counted the number of stillbirths or babies that died before reaching 1 year of corrected age, and they also counted the incidence of moderate or severe cerebral palsy at or beyond 2 years of corrected age.

The results showed that:

  • 95.6 per cent of the children were followed up.
  • Primary analysis did not show significant differences between the two groups in the combined risk of moderate or severe palsy or death (11.3 per cent in the treatment group, 11.7 per cent in the placebo group, with a relative risk of 0.97).
  • Secondary analysis showed that moderate or severe cerebral palsy occurred significantly less frequently in the magnesium sulfate group (1.9 per cent versus 3.5 per cent more cases in the placebo group, giving a relative risk of 0.55, ie 45 per cent less risk of moderate or severe cerebral palsy in the treatment group).
  • The risk of death was not significantly different between the groups.
  • Adverse events such as flushing and sweating were more common among the women in the treatment group, and none of the women experienced a life-threatening event.

The authors concluded that:

“Fetal exposure to magnesium sulfate before anticipated early preterm delivery did not reduce the combined risk of moderate or severe cerebral palsy or death, although the rate of cerebral palsy was reduced among survivors.”

An editorial in the same issue of the journal said the study showed promising results but did not recommend using magnesium sulphate in anticipated preterm labour as a way to prevent cerebral palsy.

The editors, who included Dr Fiona Stanley, from the University of Western Australia’s Centre for Child Health Research, said that more research was needed that looked more closely at the reasons for preterm birth and the effects of timing (eg relative to pregnancy weeks and birth) and size of magnesium sulphate doses.

“A Randomized, Controlled Trial of Magnesium Sulfate for the Prevention of Cerebral Palsy.”
Rouse, Dwight J., Hirtz, Deborah G., Thom, Elizabeth, Varner, Michael W., Spong, Catherine Y., Mercer, Brian M., Iams, Jay D., Wapner, Ronald J., Sorokin, Yoram, Alexander, James M., Harper, Margaret, Thorp, John M., Jr., Ramin, Susan M., Malone, Fergal D., Carpenter, Marshall, Miodovnik, Menachem, Moawad, Atef, O’Sullivan, Mary J., Peaceman, Alan M., Hankins, Gary D.V., Langer, Oded, Caritis, Steve N., Roberts, James M., the Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network.
N Engl J Med 2008, 359: 895-905.
Volume 359; pages 895-905, published online August 28, 2008.

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Sources: NEJM.

Written by: Catharine Paddock, PhD