And some previous research had found magnesium sulfate effective for reducing the risk of cerebral palsy, but other studies had been inconclusive. So, Rouse and his colleagues embarked on this large, more comprehensive study.
They found no significant differences in the proportion of deaths between the magnesium sulfate group and the placebo group. But they did find that moderate or severe cerebral palsy was diagnosed in just 1.9 percent of the group treated with magnesium sulfate, compared to 3.5 percent in the placebo group.
Rouse said it's not known for certain how the compound may work. But, he said, it may "stabilize the vessels in the vulnerable preterm brain," protect against damage from lack of oxygen, and guard against injury caused by swelling and inflammation.
"Our findings are applicable only to early preterm birth," he added. "We define high risk as threatening delivery prior to 32 weeks."
Dr. William Zinser is a pediatric neurologist at Children's Medical Center, Dallas, and an associate professor of pediatric neurology at the University of Texas Southwestern Medical Center. He said, "It's too early to know if magnesium sulfate has an overall effect on the incidence rate of cerebral palsy."
Zinser reviewed the study but was not involved with it. "More research needs to be done, certainly," he said.
Rouse said women at risk for preterm birth should discuss the potential use of magnesium sulfate with their doctors.
To learn more about preterm birth, visit the March of Dimes.
SOURCES: Dwight J. Rouse, M.D., professor of obstetrics and gynecology, University of Alabama at Birmingha
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