Interventions May Cut CP Risk in Infants

Strategies aim to lower odds for premature babies

TUESDAY, Nov. 25, 2003 (HealthDayNews) -- Two new studies raise hopes for one day being able to reduce the risk of cerebral palsy in newborns.

"It puts a little glimmer of hope that maybe we could have some tactics to prevent this very devastating neurological condition," says Dr. Larry C. Gilstrap, chairman of the department of obstetrics and gynecology at the University of Texas Medical School at Houston and co-author of an editorial accompanying the two studies, which appear in the Nov. 26 issue of the Journal of the American Medical Association.

Cerebral palsy (CP) refers to a group of conditions involving reduced ability to control movement and posture. According to United Cerebral Palsy, about 8,000 babies and infants are diagnosed with the condition each year. Cerebral palsy occurs in one to 2.4 per 1,000 live births in the United States, half in full-term infants.

Because experts don't really know what causes CP, they don't know much about how to prevent it.

"The No. 1 association with CP -- but it's hard to say if it's causative or an association -- is prematurity," Gilstrap says. "The frequency in prematurity is really high, and there's really no way to date that's been effective in preventing prematurity, with the exception of progesterone."

The first study investigated whether giving intravenous magnesium sulfate to women who were just about to deliver a premature baby (before 30 weeks' gestation) reduced the risk of neurosensory impairments such as CP.

Observational studies have indicated that magnesium sulfate may have a benefit, but there have been no rigorous clinical trials to confirm this.

The current study, the largest of its kind, took place at 16 hospitals in Australia and New Zealand and involved 1,062 women who planned or expected to give birth within the next 24 hours. The women were randomly assigned to receive either magnesium sulfate or a placebo consisting of sodium chloride. Their surviving children were followed for two years.

When data was analyzed for 1,047 of the two-year survivors, the researchers found a pediatric mortality rate of 13.8 percent in the magnesium sulfate group vs. 17.1 percent in the control group. The rate of CP was 6.8 percent in the magnesium sulfate group vs. 8.2 percent in the control group. The combined rate of death or CP was 19.8 percent in the intervention group and 24.0 percent in the control group. Overall, this represented a reduction of 17 percent in the intervention group.

It's unclear exactly how magnesium sulfate might protect a baby's brain.

"The NIH is currently doing another huge study that'll be done fairly soon, and if that substantiates what's in this study from Australia, that would be a big impact," Gilstrap says.

The second study found that a condition called chorioamnionitis, or an inflammation of the placental membranes, is associated with a fourfold greater risk of CP among newborn infants.

The study authors looked at 109 infants with moderate-to-severe CP and 218 healthy babies born at 36 weeks or more in the Kaiser Permanente Medical Care Program in northern California.

Infection had been diagnosed in 14 percent of the mothers who gave birth to children with CP and in 4 percent of those with healthy babies.

At this point, all researchers have is an association and not any kind of cause-and-effect relationship, says the study's lead author, Dr. Yvonne Wu, an assistant professor of neurology and pediatrics at the University of California San Francisco School of Medicine.

No one knows, she adds, whether the infection or inflammation causes the injury or simply makes the brain more vulnerable to injury during delivery. "It's not clear," she says.

And because the results are preliminary, researchers are still a long way from a solution.

"The findings imply that if inflammation is a factor that there may be something we can do to interrupt the inflammation pathways, but we're still pretty far from knowing what those things are," Wu says. Some of the proteins involved in the inflammation response are important to brain development, so no one wants to mess with them without knowing exactly what the effect will be.

One positive step would be to find a better way to diagnose chorioamnionitis, Wu proposes.

Wu and her colleagues also found that intrauterine growth restriction was associated with a fourfold greater risk of CP, black ethnicity in the mother was associated with a 3.6 times increased risk, mothers older than 25 had a 2.6 times increased risk, and first births had a 1.8 times greater risk of CP.

More information

For more on this condition, visit United Cerebral Palsy or the National Institute of Neurological Disorders and Stroke.

SOURCES: Larry C. Gilstrap, M.D., chairman, department of obstetrics and gynecology, University of Texas Medical School, Houston; Yvonne W. Wu, M.D., assistant professor of neurology and pediatrics, University of California, San Francisco; Nov. 26, 2003, Journal of the American Medical Association
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