When a woman experiences premature labor during pregnancy, she may be given an intravenous treatment of magnesium sulfate as a means of delaying labor and preventing premature delivery.  A new study reveals the treatment may come with an added bonus - using magnesium to delay premature labor reduces the baby’s risk of developing cerebral palsy.

Cerebral palsy is a collective term for a group of neurological disorders that affect a person’s ability to control his or her own movements and posture, a situation that limits all activities.  The disorder may stem from injury or developmental abnormalities that occur during pregnancy, delivery, and in the earliest stages of childhood.  About one-third of all cases of the disorder are traced to premature births although the exact causes of the disorder remain poorly understood.

Magnesium sulfate works in several ways that may protect an endangered child from developing the neurological disorder.  It helps stabilize blood vessels, limits damage caused by oxygen depletion, and it protects against injuries that might be caused by inflammation and swelling.

In several studies dating back to 1995, research has suggested a lower rate of cerebral palsy in preterm babies whose mothers were given magnesium sulfate when premature labor commenced.  Armed with this background information, federal investigators at 20 research centers affiliated with the Maternal Fetal Medicine Units Network conducted what they describe as the largest and most comprehensive study to date to explore the link between cerebral palsy and magnesium sulfate administered during pregnancy.

The Maternal Fetal Medicine Units Network is a part of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the National Institutes of Health (NIH).  Funded in part by NIH’s National Institute of Neurological Disorders and Stroke, the study was led by Dwight J. Rouse, MD, of the University of Alabama at Birmingham.

All women participating in the study reported to one of the 20 research centers between the 24th and 31st weeks of gestation and all were experiencing premature labor.  Each woman was chosen at random to receive either magnesium sulfate or a placebo.  The dosage for magnesium sulfate was 6 grams during the first 20 to 30 minutes of labor, with an additional 2 grams administered every hour for 12 hours or until they gave birth, or until labor stopped.  In the cases where labor stopped, treatment was repeated in all cases where labor started again before the 34th week of the pregnancy.

The research team monitored the children born of these women for symptoms of cerebral palsy, which they categorized in one of three ways - those with moderate cases, those with severe cases, and those who died.  Mild cases of the disorder were not evaluated for study purposes because mild cases of cerebral palsy have a tendency to correct themselves over time.

Using various factors for calculation, the research team reports these findings:

• When grouping together all moderate and severe cases of cerebral palsy, the group getting magnesium sulfate experienced the disorder at a rate of 1.9% versus 3.5% in the control group.
• 41 children born from the 942 pregnancies in which magnesium sulfate was administered were diagnosed with cerebral palsy, up from the 74 cases of cerebral palsy in the 1,002 pregnancies in the control group.
• In the group treated with magnesium sulfate, 2.2% of the cerebral palsy cases were identified as mild, 1.5% as moderate, and 0.5% were diagnosed as severe.
• In the placebo, or control, group, 3.7% developed mild cases of cerebral palsy, 2.0% had moderate cases, and 1.6% were severe.
• The rate of death in either group was statistically insignificant, with a 9.5% death rate in the treated group and 8.5% in the placebo group.
• The average gestational age differed little, if at all, between the two study groups.

Magnesium sulfate is readily available and obstetricians are familiar with its use, two situations the research team considers instrumental when trying to avoid the severe medical complications that can arise from a preterm delivery.

The study is presented in full in the August 28 issue of the New England Journal of Medicine.