Rates of cerebral palsy have remained nearly flat for decades, despite an increase in obstetric interventions.

But a new study involving University of Utah researchers concludes that giving intravenous magnesium sulfate to women at risk of preterm birth significantly reduces the risk for cerebral palsy.

Results of the multi-center study, which included many Utah women, will be published Thursday in The New England Journal of Medicine.

Dr. Michael W. Varner, professor and vice chairman for research in the Department of Obstetrics and Gynecology at the U. and a study co-investigator, describes cerebral palsy as a nonprogressive impairment of neuromuscular function that's often associated with various degrees of neuropsychological delay. And he notes that while most of the babies born with cerebral palsy are full-term and had uncomplicated deliveries, among women at risk of premature delivery, the decrease associated with magnesium sulfate is striking.

The study looked at 2,241 women at risk of preterm birth, 86 percent of whom had experienced premature membrane rupture. They were randomly assigning them to receive a placebo or magnesium sulfate. Of the women who received the magnesium compound, 4.2 percent had a form of cerebral palsy, compared to 7.3 percent of those who received a placebo. Of those with moderate to severe cerebral palsy, 1.9 percent received the drug compared to 4.6 percent in the placebo group.

Magnesium sulfate is often used to prevent seizures in women with pre-eclampsia and to stop early labor. Observation and a look back at data suggested it might impact the number of women whose babies had cerebral palsy by age 2. But with a retrospective study, "it's hard to tell if you're comparing apples and apples, different types of apples or apples and oranges," he said. A prospective study was needed.

Preterm birth is a known risk factor for cerebral palsy. Because the numbers are small at any one location, the National Institutes of Health, which helped fund the study, relied on its well-established maternal-fetal medicine network, with 19 centers — including the U. — to get enough data to study to the issue. Not only was the U. a major contributor, but it has a noteworthy and very successful research collaboration with Intermountain Healthcare that meant most high-risk pregnancies in the area were included. Information was included from University Hospital, McKay-Dee in Ogden, LDS Hospital in Salt Lake City and Utah Valley Regional Medical Center in Provo.

"I think we represent well the spirit of academic community collaboration," Varner said of the partnership.

Women at high risk of premature delivery who agreed to participate were given the medicine or placebo between 24 and 31 weeks. Those who didn't deliver at the time of the membrane rupture were given another infusion of the same solution when they did deliver. The surviving babies were reevaluated at 6, 12 and 24 months. They had a two-year follow up on about 96 percent of the surviving kids, he noted.

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