Preterm labor drug side effects evaluated

A U.S. study says magnesium sulfate, a common preterm labor drug, is more likely to cause side effects in pregnant women than other alternatives.

The report by researchers at Lucile Packard Children's Hospital and Stanford University School of Medicine said newborns whose mothers had received magnesium sulfate also were more likely to be admitted to the neonatal intensive care unit than those whose mothers had received nifedipine.

The researchers, however, warn that none of the currently available treatments for preterm labor are perfect.

"There is no free lunch with any of these drugs," Dr. Deirdre Lyell said Friday in a news release. "But magnesium sulfate has some particularly unpleasant side effects, including vomiting, lethargy and blurry vision. The alternative treatment, nifedipine, often leaves women feeling better."

A study of 192 patients at Packard Children's or Santa Clara Valley Medical Center who were in preterm labor found magnesium sulfate was more effective in stopping contractions but there were no significant differences in the treatments' ability to delay delivery.

The researchers speculate that nifedipine, rather than stopping a woman's contractions, simply renders them clinically ineffective.