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January 2005 Issue

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Study Confirms Risk During Delivery After C-Section

Published January 2005

A nationwide study of women who chose vaginal delivery after previously undergoing a cesarean section shows that the often-debated complications are possible, although the absolute risk is small.

A report of the study done at 19 academic medical centers, including the University of Cincinnati, appears in the Dec. 16 issue of The New England Journal of Medicine.

One of the major risks in vaginal birth after cesarean section (VBAC) is symptomatic uterine rupture. Although it occurred in less than 1 percent (124 women or 0.7 percent) of VBAC cases, the study confirmed an increased risk of uterine rupture, regardless of the method of induction employed.

This, according to UC's Baha Sibai, MD, is the most significant aspect of the study. Women should know that if they opt for "trial of labor" after a previous cesarean section, they risk causing brain damage to their baby in the event of a uterine rupture.

While the risk to the mother is about the same with cesarean section and trial of labor, and the risk of uterine rupture and subsequent fetal brain damage is low, Dr. Sibai says, "It's very difficult to understand why any patient would accept it."

Dr. Sibai, chairman of UC's Department of Obstetrics and Gynecology, participated in the study both in his current position in Cincinnati and at his previous appointment at the University of Tennessee.

Conducted between 1999 and 2002, the study involved about 46,000 women who had undergone prior cesarean delivery. About 16,000 of these women underwent elective, repeat cesarean delivery without labor, another 18,000 attempted VBAC, and about 12,000 more had other maternal or fetal indications for a repeat cesarean delivery.

The study results showed that compared with elective repeat cesarean delivery, women attempting VBAC are at increased risk for maternal morbidity and serious obstetric complications, such as uterine rupture, endometritis, and transfusion or newborn hypoxic ischemic encephalopathy (HIE), a type of newborn brain injury due to lack of oxygen. About 39 percent of the women chose to attempt a vaginal delivery in spite of their previous cesarean section. Of these, 73 percent succeeded in trial of labor and delivered vaginally.

Among infants whose mothers chose trial of labor, the frequency of hypoxic ischemic encephalopathy was increased. While only 12 cases of HIE occurred with labor, there were no cases among women who elected to have a repeat cesarean delivery.

Seven of 12 cases of HIE, including two neonatal deaths, followed uterine rupture. Maternal morbidity, endometritis and blood transfusion were all more likely among women who chose VBAC than among those who chose repeat cesarean delivery.

"This study is significant in addressing an issue that continuously receives debate in obstetrics," says Mark Landon, MD, principal investigator for the four-year study and vice chairman of obstetrics and gynecology at Ohio State University Medical Center.

"Until now, the information comparing a trial of labor and an elective repeat operation has been inadequate to counsel women concerning their options for childbirth following prior cesarean delivery.

"While the magnitude of these risks for serious complications is small, women who have had a previous cesarean section and who are considering choices for childbirth should be aware of the level of risk involved," Dr. Landon says. "Overall the risk for a serious newborn complication is approximately 1 in 2,000 trials of labor. At this level of risk, many women will continue to opt for an attempted VBAC. The benefits of this approach would be faster recovery, shorter hospital stay and avoiding the risks of major surgery."

In past studies of VBAC and cesarean sections, the risk has remained uncertain. Terminology and definitions for uterine rupture varied significantly, and the lack of direct evidence about benefits and risks has made it difficult for physicians to provide appropriate counseling.

"The picture has been anything but clear," says Dr. Landon.

The study was sponsored by the National Institute of Child Health and Human Development.

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