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Risk Seen in Vaginal Delivery After C-section

Induced labor raises risk of womb rupture

THURSDAY, July 5, 2001 (HealthDayNews) -- Women who've already had a Cæsarean section are more likely to suffer a ruptured womb in a subsequent delivery if labor is induced with certain hormone-like drugs, a new study says.

The study of 20,095 Washington state mothers found that uterine rupture is roughly 15 times more common after induction of labor with prostaglandins than women who have a repeat C-section.

Babies born to women who suffer a burst uterus face a ten-fold increased risk of death in the period surrounding delivery. The findings are reported in todays New England Journal of Medicine.

"If the only consideration is the relative risk to the fetus, then there's no doubt that" the chances for harm are lowest with an elective repeat Csarean section, says Dr. Michael Greene, a maternal health expert at Massachusetts General Hospital in Boston and author of an accompanying editorial in the journal.

However, Greene says the absolute chance of complications is essentially "trivial," so many women may choose to shrug off the theoretical risk.

Researchers have known for decades that vaginal delivery after a C-section can rupture a uterus weakened by scar tissue from the earlier operation. But previous studies haven't been large enough to show whether that risk increases in women who later have labor induced.

Government figures show that induced labors have increased dramatically, from 9.5 per 100 live births in 1990 to nearly 20 per 100 live births in 1999.

The latest study, led by University of Washington nursing researcher Mona Lydon-Rochelle, compared rates of uterine rupture among expectant mothers who'd had a previous single baby delivered by cesarean section. Some women had spontaneous, vaginal deliveries; some opted for second C-sections, and some had labor induced either with prostaglandins or with other methods that trigger contractions.

Overall, 91 women suffered ruptured wombs, a rate of 4 to 5 per 1,000 women. The rate of rupture was 5 per 1,000 for women who had spontaneous vaginal delivery, compared with just 1.6 per 1,000 among those who had a C-section.

But for women given prostaglandins, the rate was more than 24 per 1,000, the researchers say, or three times as those induced with other means.

"Women need to be aware that a trial [or vaginal] labor increases their chances of uterine rupture, especially with prostaglandins," Lydon-Rochelle says. On the other hand, she says the researchers aren't making any recommendations about whether women should forgo vaginal delivery in favor of a second C-section, since the surgical procedure carries a small but definite risk of complications and even death.

Scientists aren't sure why prostaglandins raise the risk of womb problems. Greene says the hormone-like molecules, which are produced naturally in the brain, are intended as cervix softeners, not as labor inducers, though they are often used that way.

They are much more potent than oxytocin, the conventional labor-inducing compound, yet they stay in the body longer and are harder to regulate, Greene says.

What To Do

For more birth statistics, check the Centers for Disease Control and Prevention.

For more on uterine rupture, try

SOURCES: Interviews with Mona Lydon-Rochelle, Ph.D., senior research fellow, University of Washington School of Nursing, Seattle, and Michael Greene, M.D., director of maternal-fetal medicine, Massachusetts General Hospital, Boston; July 5, 2001, New England Journal of Medicine
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