ObjectivesTo investigate the association between the geometrical properties of episiotomy and obstetric anal sphincter injuries (OASIS) because episiotomies angled at 40–60° are associated with fewer OASIS than episiotomies with more acute angles.DesignCase–control study.SettingUniversity Hospital of North Norway, Tromsø and Nordland Hospital, Bodø, Norway.SampleSeventy-four women who had one vaginal birth and episiotomy. Cases (n = 37) have sustained OASIS at birth, while controls (n = 37) had not. The groups were matched for instrumental delivery.MethodsTwo groups of women with history of only one vaginal birth were compared. Episiotomy scar was identified and photographed and relevant measures were taken. Data were analysed using conditional logistic analysis.Main outcome measuresMean episiotomy angle, length, depth, incision point.ResultsThe risk of sustaining OASIS decreased by 70% (odds ratio [OR] 0.30; 95% CI 0.14–0.66) for each 5.5-mm increase in episiotomy depth, decreased by 56% (OR 0.44; 95% CI 0.23–0.86) for each 4.5-mm increase in the distance from the midline to the incision point of the episiotomy, and decreased by 75% (OR 0.25; 95% CI 0.10–0.61) for each 5.5-mm increase in episiotomy length. Lastly, there was no difference in mean angle between groups but there was a “U-shaped” association between angle and OASIS (OR 2.09; 95% CI 1.02–4.28) with an increased risk (OR 9.00; 95% CI 1.1–71.0) of OASIS when the angle was either smaller than 15°or >60°.ConclusionThe present study showed that scarred episiotomies with depth > 16 mm, length > 17 mm, incision point > 9 mm lateral of midpoint and angle range 30–60° are significantly associated with less risk of OASIS. Shrinkage of tissue must be considered.

Objective To evaluate and compare the risk profile of sustaining obstetric anal sphincter injuries (OASIS) and associated risks in five risk groups (low to high), after the OASIS rate was reduced from 4.6% to 2.0% following an interventional programme. The main focus of the intervention was on manual assistance during the final part of second stage of labour.Design A multicentre interventional cohort study with before and after comparison.Setting Four Norwegian obstetric departments. after the intervention. Associations with obstetric risks for OASIS were largely unchanged after the intervention, including first vaginal delivery (OR 3.84; 95% CI 2.90-5.07), birthweight 4500 g (OR 4.42; 95% CI 2.68-7.27), forceps delivery (OR 3.54; 95% CI 1.99-6.29) and mediolateral episiotomy (OR 0.89; 95% CI 0.70-1.12). However, the highest reduction of OASIS, (65%), was observed in group 0 (low-risk) (OR 0.35; 95% CI 0.24-0.51), and a 57% (OR 0.43; 95% CI 0.35-0.52), 61% (OR 0.39; 95% CI 0.31-0.48), and 58% (OR 0.42; 95% CI 0.30-0.60) reduction in groups with one, two and three risk factors, respectively. No change was observed in the group with four risk factors.Conclusion After the intervention the most significant decrease of OASIS was observed in low-risk births, although the main risk factors for OASIS remained unchanged.Keywords Low-risk deliveries, manual assistance, obstetric anal sphincter injuries, risk factors.Please cite this paper as: Stedenfeldt M, Øian P, Gissler M, Blix E, Pirhonen J. Risk factors for obstetric anal sphincter injury after a successful multicentre interventional programme. BJOG 2014;121:83-91.

BackgroundObstetric anal sphincter injuries (OASIS) might cause anal incontinence (AI) and sexual dysfunction, and might be associated with urinary incontinence (UI). Episiotomy has been identified both as a risk and a protective factor of OASIS. Lately, episiotomies with specific characteristics have shown to be protective against the risk of OASIS. However, little is known about episiotomy characteristics and pelvic floor dysfunction. This study investigates AI, UI, and sexual problems in primiparous women with episiotomy, comparing women with and without OASIS. Associations between episiotomy characteristics and AI, UI, and sexual problems were assessed.MethodsThis is a matched case–control study investigating 74 women with one vaginal birth, all with an episiotomy. Among these, 37 women sustained OASIS and were compared to 37 women without OASIS. The two groups were matched for vacuum/forceps. AI, UI and sexual problem symptoms were obtained from St. Mark’s scoring-tool and self-administered questionnaires. The episiotomy characteristics were investigated and results assessed for the whole group.ResultsThe mean time from birth was 34.5 months (range1.3-78.2) for those with OASIS and 25.9 months (range 7.0-57.4) for those without OASIS, respectively. More women with OASIS reported AI: 14 (38%) vs. 3 (8%) p = 0.05 (OR 4.66, 95% CI 1.34-16.33) as well as more problem with sexual desire p = 0.02 (OR 7.62, 95% CI 1.30-44.64) compared to women without OASIS. We found no association between episiotomy with protective characteristics and dysfunctions.ConclusionWomen with OASIS had more AI and sexual problems than those without OASIS. Episiotomy characteristics varied greatly between the women. Episiotomy with protective characteristics was not associated with increased dysfunctions. OASIS should be avoided, and correct episiotomy used if indicated.