Sphincter tear rate falling in vaginal births.(Obstetrics)

TUCSON, ARIZ. -- The rate of anal sphincter laceration during vaginal delivery has declined sharply in recent years, paralleling modifications in obstetric practice, a University of Southern California study revealed.

Anal sphincter laceration occurred in 11.2% of vaginal deliveries at the colossal Los Angeles County / USC Medical Center in 1996, compared with 7.9% in 2004, with about a 6% reduction in risk every year after 1996, reported Dr. Steven Minaglia at the annual meeting of the Society of Gynecologic Surgeons.

"Changes in obstetric practice, such as the increase in cesarean section and the decrease in operative delivery and episiotomy, may have contributed to the dramatic reduction in sphincter laceration," Dr. Minaglia said.

During the time period studied, episiotomies declined from 9% to 8% of vaginal deliveries, vacuum deliveries from 5.1% to 2.9%, and forceps deliveries from 1.7% to 0%. "Of note, the C-section rate went from 18.2% to 32.3%," he said.

The retrospective study assessed characteristics in 1,703 patients who had an anal sphincter laceration and 14,964 who did not have such an injury, for a total of 16,667 singleton vaginal deliveries at greater than 20 weeks of gestation. Younger age, lower parity, and higher birth weight all were associated with a higher likelihood of an anal sphincter laceration.

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