Jan. 31 (HealthDay News) -- An infusion of Epsom salt (magnesium sulfate) given just before delivery to pregnant women at high risk for preterm birth cut the rate of cerebral palsy among these newborns in half, U.S. researchers report.

The study included 2,241 women at 20 sites across the United States. All the women were at high risk for giving birth prematurely -- between 24 and 31 weeks into their pregnancies. The women were randomly selected to receive either an intravenous infusion of magnesium sulfate solution or a placebo.

The infusions, started when delivery seemed imminent, began at a rate of 6 grams infused over 20 to 30 minutes, followed by a maintenance infusion of 2 grams per hour. If delivery didn't occur within 12 hours, the infusion was halted and resumed later when delivery once again seemed about to happen.

There was no significant difference in the risk of infant death between the women who received the magnesium sulfate and those who received the placebo. However, moderate or severe cerebral palsy occurred about half as often in infants born to women in the magnesium sulfate group (1.9 percent), compared to those in the placebo group (3.5 percent).

"This is one of the most promising breakthroughs in the management of high-risk pregnancies in more than 30 years," study co-author Dr. John Thorp, a professor of obstetrics and gynecology at the University of North Carolina in Chapel Hill, said in a prepared statement.

He noted that "virtually every delivery room in the United States is already stocked with magnesium sulfate solutions that are given to pregnant women during childbirth for other reasons."

"So, what we have learned from this study is that we have a cheap, widely available treatment already in hand that cuts in half the risk of babies being born with an extremely disabling disorder. This is a tremendously exciting development," Thorp said.

The findings were expected to be presented Thursday at the Society for Maternal-Fetal Medicine annual meeting, in Dallas. The study was conducted for the Maternal-Fetal Medicine Units Network of the U.S. National Institute of Child Health and Human Development.

SOURCE: Public Communications Inc., news release, Jan. 31, 2008