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Vaginal delivery after prior c-section remains relatively safe

A woman who has delivered a baby by cesarean section has an increased risk of uterine rupture due to uterine scarring if she attempts a vaginal birth with the next child. However, the risk of uterine rupture is low enough (.5 percent) that vaginal birth after cesarean (VBAC) remains a relatively safe procedure, concludes a study supported in part by the Agency for Healthcare Research and Quality (contract 290-90-0039, Childbirth Patient Outcomes Research Team, PORT). The study findings support recommendations by the National Institutes of Health and the Department of Health and Human Services to reduce cesarean rates by widespread VBAC.

The researchers used California hospital discharge data for over 500,000 women delivering babies in the State in 1995 to calculate attempted and successful VBAC rates and uterine rupture rates. The overall cesarean rate was 21 percent, and 12.5 percent of the women had histories of cesareans. Of women with prior cesareans, 61 percent attempted VBAC, and 35 percent were successful. The uterine rupture rate was 0.07 percent for all deliveries and 0.43 percent for women with prior cesareans who attempted VBAC. Although a woman's ethnicity and payer source were independent risk factors for cesarean, they did not appear to be risk factors for uterine rupture, according to first author Kimberly D. Gregory, M.D., M.P.H.

Among women with prior cesareans, those who attempted a trial of labor were nearly twice as likely to have uterine rupture as women who did not attempt vaginal delivery. Women who delivered in hospitals with higher attempted VBAC rates were 20 percent less apt to have cesarean deliveries, 17 percent more likely to have successful VBACs, and 56 percent more likely to experience uterine rupture. Overall, California's 35 percent rate of successful VBACs was higher than the 25 percent national average. However, the overall uterine rupture rate for all women and those with prior cesareans was similar to previous estimates.

See "Vaginal birth after cesarean and uterine rupture rates in California," by Dr. Gregory, Lisa M. Korst, M.D., Patricia Cane, Ph.D., and others, in the December 1999 Obstetrics and Gynecology 94(6), pp. 985-989.

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