Risk factors for obstetric anal sphincter injury after a successful multicentre interventional programme

Authors

  • M Stedenfeldt,

    Corresponding author
    1. The Norwegian Continence and Pelvic Floor Centre, University Hospital of North Norway, Tromsø, Norway
    2. Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway
    • Correspondence: M Stedenfeldt, The Norwegian Continence and Pelvic Floor Centre, P.O.Box 96, N-9038 University Hospital of North Norway, Tromsø, Norway. Email mona.stedenfeldt@unn.no

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  • P Øian,

    1. Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway
    2. Department of Obstetrics and Gynaecology, University Hospital of North Norway, Tromsø, Norway
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  • M Gissler,

    1. National Institute for Health and Welfare (THL), Helsinki, Finland
    2. Nordic School of Public Health, Gothenburg, Sweden
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  • E Blix,

    1. Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway
    2. Department of Clinical Research, University Hospital of North Norway, Tromsø, Norway
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  • J Pirhonen

    1. The Norwegian Continence and Pelvic Floor Centre, University Hospital of North Norway, Tromsø, Norway
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Abstract

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.

Sample

A total of 40 154 vaginal deliveries in 2003–09.

Methods

Pre-intervention and postintervention analyses. The associations of OASIS with possible risk factors were estimated using odds ratios obtained by logistic regression.

Main outcome measure

Risk factors of OASIS.

Results

The risk of sustaining OASIS decreased by 59% (odds ratio [OR] 0.41; 95% confidence interval [95% CI] 0.36–0.46) 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.

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