Once a cesarean, always a cesarean?

About one in four U.S. babies is born by cesarean section. In the past, physicians counseled women who had delivered a baby by this surgery to do the same in subsequent births. Now, roughly 60 percent of women in the United States whose first baby is born by cesarean shun that route the second time, opting instead to go into labor to attempt a vaginal delivery.

A study of more than 20,000 women in Washington State now finds that expectant mothers who've already given birth by cesarean section put themselves at increased risk of uterine rupture by trying vaginal birth, particularly if physicians induce the labor.

The study, in the July 5 NEW ENGLAND JOURNAL OF MEDICINE, reveals that such women had more than three times the incidence of uterine rupture than did similar women who avoided labor and had another cesarean. That's a chance of 5.2 ruptures per 1,000 vaginal births, compared with 1.6 ruptures per 1,000 in the cesarean-only group, report Diane P. Martin, an epidemiologist at the University of Washington in Seattle, and her colleagues.

In cases where doctors induced labor with such drugs as oxytocin and misoprostol, the uterine-rupture rate rose to 7.7 per 1,000. When physicians administered the hormonelike drug prostaglandin to induce labor, the rate of ruptures soared to 24.5 ruptures per 1,000 deliveries.

Cesarean delivery poses more health risks in general, causes greater postpartum discomfort, and requires longer recovery time than vaginal delivery does. Nevertheless, the new study suggests that women who elect vaginal birth after a cesarean section are taking an unnecessary risk, comments physician Michael F. Greene of Massachusetts General Hospital in Boston in the same journal.