Study: Labor Risk After C-Section

ByDan Childs

B O S T O N, July 5, 2001 -- Pregnant women who have had previous Caesarean sections have less of a risk of dangerous uterine rupture if they opt for a C-section again rather than undergo a vaginal delivery, according to a new study.

A Caesarean section is a surgical procedure in which the baby is removed through an incision in the mother's abdomen. About 20 percent of women currently choose the operation over traditional vaginal delivery.

A uterine rupture, or when the uterus splits open during labor, can be dangerous for the mother because it can result in massive blood loss. It can also put the baby in danger of death or brain damage by depriving it of oxygen. However, uterine ruptures are quite rare, occurring in only a few out of every thousand births, including vaginal births and vaginal births after a C-section.

Uterine Rupture Risk Increases

Mona Lydon-Rochelle, a researcher at the University of Washington and lead author of the study appearing in this week's New England Journal of Medicine, found that women who have had a C-section have three times the chance of uterine rupture if they choose natural labor on their next birth.

And when the labor is induced with uterus-relaxing hormones called prostaglandins, the risk of rupture is 15.6 times than that of a C-section.

"The take-home message is that induction of pregnancy with prostaglandins is associated with an increase in the chance of uterine rupture," Lydon-Rochelle said.

Vaginal birth after a C-section increases the chances of uterine rupture because muscle contractions produced by labor put strain on the scar from the C-section. A second C-section lessens the risk of rupture by avoiding the muscle contractions associated with labor altogether, resulting in less strain on the uterus.

"Most women who have had a Cesarean do successfully undergo a trial of labor without a uterine rupture, but what we've seen is that the child's labor becomes much more dangerous when it is induced with prostaglandins," Lydon-Rochelle said.

C-Sections Still Risky

But because uterine ruptures are so rare, occurring in just 2.5 percent of cases even when prostaglandins are used, experts question whether pregnant women should expose themselves to the dangers of surgery.

"The safest thing for the baby is for the mother to have a C-section, and that's inarguable," said Dr. Peter Schwartz, chairman of the American College of Obstetricians and Gynecologists. "But it appeared to me as I ran the numbers that you would have to perform 2,500 C-sections to save one baby. When you're talking about C-sections, there is a risk to the mother of bleeding, infection, and other side effects of the incision.

"A C-section is relatively safe [for the mother], but it's not as safe as a vaginal delivery, and to do 2,500 of them to save one baby must be weighed."

Lydon-Rochelle said because of the balance between risks to the mother and baby, an individualized approach is needed.

"All we can say is that if a health care provider is talking to a woman about labor after a C-section, based on these findings, they would want to discuss with her the increased chances of uterine rupture," she said.

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