Study Suggests Ways to Reduce Anal Sphincter Injuries Associated With Episiotomies


New research suggests episiotomy guidelines that may help reduce the risk of obstetric anal sphincter injuries.

New research suggests episiotomy guidelines that may help reduce the risk of obstetric anal sphincter injuries. M Stedenfeldt of the Norwegian Continence and Pelvic Floor Centre at the University Hospital of North Norway, Troms, Norway, and colleagues published their findings in a recent issue of BJOG:An International Journal of Obstetrics and Gynaecology.

Stedenfeldt and colleagues conducted a case control study of women who had one vaginal birth in which they received an episiotomy (N=74). The cases included women who experienced obstetric anal sphincter injuries, which made up about half of the study population (n=37). The researchers matched cases and controls in regards to instrumental delivery. The study noted episiotomy scars and related measures, specifically looking at mean episiotomy angle, length, depth, and incision point.

According to the data collected, the risk of obstetric anal sphincter injuries decreased by 70% for each 5.5 mm increase in episiotomy depth and decreased by 56% for each 4.5 mm increase in the distance from the midline to the incision point of the episiotomy. Stedenfeldt et al. also found that the risk of these injuries decreased by 75% for each 5.5 mm increase in episiotomy length. The researchers failed to find a difference in mean angle between the women in the case group as compared to the women in the control group. However, they did find there was a “U-shaped” association between obstetric anal sphincter injuries and angle of episiotomy, with an odds ratio of 2.09; specifically, when the angle was smaller than 15 degrees or larger than 60 degrees, the odds ratio increased to 9.0 .

“Depth and episiotomy length were the most significant characteristics associated with less risk of OASIS [obstetric anal sphincter injuries] when compared with incision point,” Stedenfeldt and colleagues concluded. “Our findings might indicate that to unload the perineum sufficiently the episiotomy must obtain a certain length and depth.”

The authors noted that their study results can help clinicians, as these guidelines can potentially result in a reduction of obstetric anal sphincter injuries. “Episiotomy technique is a modifiable procedure, and it is therefore important to make note of the parameters referred to in this study,” they explained.


Stedenfeldt M, Pirhonen J, Blix E, et al. Episiotomy characteristics and risks for obstetric anal sphincter injuries: Hitt E. Episiotomy parameters linked to risk for injury during birth. Medscape News. March 2012.

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