WASHINGTON -- The incidence of cerebral palsy in babies with very low birthweight was substantially lower among those whose mothers received injections of a certain drug in the hours before giving birth, two new studies show.
The drug is an inexpensive natural chemical, magnesium sulfate, that obstetricians often inject as an intravenous infusion when a woman goes into labor prematurely. The intention is to try to stop the labor and to prevent convulsions from pre-eclampsia, a serious complication of pregnancy.
The findings came from observational studies of children born in four counties in Northern California and at the University of Alabama in Birmingham.
Their mothers had received magnesium sulfate for medical reasons, not to prevent cerebral palsy. Thus, researchers cautioned that proof that magnesium sulfate prevented cerebral palsy would require more studies, such as randomly giving magnesium sulfate to some pregnant women and not others.
But Dr. Karin B. Nelson, an epidemiologist at the National Institute of Neurological Disorders and Stroke in Bethesda, Md., said in an interview that the findings suggested that a wider use of magnesium sulfate could prevent an estimated 1,000 cases of cerebral palsy, or one-sixth of all such cases that occur every year.
Dr. Nelson was a co-author of the Northern California study, which was sponsored by her institute. She carried out the research with Dr. Judith K. Grether of the California Birth Defects Monitoring Program of the state Department of Health Services.
Findings from the Nelson-Grether study are being reported in today's issue of Pediatrics, published by the American Academy of Pediatrics.
Cerebral palsy is a birth disorder of unknown cause that produces permanent damage to motor nerves, resulting in varying degrees of paralysis and other neurological problems.
According to the latest available data, which is about 10 years old, some 5,500 moderate and severe cerebral palsy cases occur in the United States each year, as measured among infants who survive for three years.
More than 25 percent of cerebral palsy cases occur among the 52,000 very low birthweight babies born every year. Low birthweight babies are those who weigh less than 1,500 grams, or 3.3 pounds. Such babies are 100 times more likely to have disabling cerebral palsy than infants weighing 6 pounds or more.
It takes two to three hours for magnesium sulfate to reach the fetus after it is injected into a pregnant woman. The researchers said they had not determined how much and at what time during pregnancy magnesium sulfate should be given. Nor do they know why magnesium sulfate apparently prevents cerebral palsy.
Magnesium is pivotal in the transfer, storage and use of energy in the body. The researchers speculated that magnesium might be important for brain development and might prevent bleeding in the brain in premature infants.
Magnesium is in such foods as green vegetables, beans and meat.