Preterm Cesareans Double Uterine Rupture Risk

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MIAMI BEACH — Women with a history of preterm cesarean delivery are twice as likely to experience uterine rupture during a subsequent vaginal delivery, compared with women who have a history of operative delivery at term, according to a large study.

However, the absolute increased risk of 1% may be acceptable to some women who are considering a trial of labor after a previous cesarean section, Dr. Anthony Sciscione said at the annual meeting of the Society for Maternal-Fetal Medicine.

"The 1% may be too high for some women but acceptable to others." Dr. Sciscione, chief of obstetrics at Crozer-Chester Medical Center in Upland, Pa., and his associates compared 5,839 women with a history of preterm cesarean delivery to 35,528 with a history of term cesarean delivery.

They found the preterm group twice as likely to experience uterine rupture on a subsequent vaginal delivery, compared with the term group (odds ratio 2.05).

The risk was still increased when the researchers controlled for emergency cesarean deliveries (OR 1.73).

"Rate of uterine rupture was highest among those who had a previous preterm delivery and subsequent full-term delivery," said Dr. Sciscione, who presented the findings on behalf of the Maternal-Fetal Medicine Units Network of the National Institute of Child Health and Human Development, Bethesda, Md.

A delivery between 20 weeks of gestation and 36 weeks, 6 days was considered preterm. The two groups were similar, but the prior preterm delivery group was younger (mean 28.6 years versus 29.2 years) and less likely to have private insurance.

Women with a previous preterm cesarean delivery were also more likely to experience earlier uterine rupture (mean 37.2 weeks) than were women with a previous term cesarean (mean 39.1 weeks).

A meeting attendee asked if the women who had uterine rupture earlier were also in labor earlier.

"That is a good question," Dr. Sciscione said. "We looked at that, but the data are not ready yet.

"Further study is needed to define those clinical characteristics which may accompany preterm cesarean delivery that may modify the risk for subsequent uterine rupture," Dr. Sciscione said.