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BMJ Open. 2012; 2(5): e001649.
Published online 2012 October 17. doi:  10.1136/bmjopen-2012-001649
PMCID: PMC3488722
Copyright © 2012, Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
Incidence of obstetric anal sphincter injuries after training to protect the perineum: cohort study
Katariina Laine,1,2 Finn Egil Skjeldestad,3 Leiv Sandvik,4 and Anne Cathrine Staff2,5
1Department of Obstetrics, Oslo University Hospital, Ullevål, Oslo, Norway
2Faculty of Medicine, University of Oslo, Oslo, Norway
3Women's Health and Perinatology Research Group, Department of Clinical Medicine, University of Tromsø, Tromsø, Norway
4Unit of Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway
5Department of Gynaecology, Oslo University Hospital, Ullevål, Oslo, Norway
Correspondence to Dr Katariina Laine; kattiksen/at/yahoo.no
Received June 11, 2012; Accepted September 4, 2012.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.
Abstract
Objective
To compare the incidence of obstetric anal sphincter injuries (OASIS) in two time periods, before and after implementing a training programme for improved perineal support aimed at reducing the incidence of obstetric anal sphincter injuries. The secondary aim was to study incidence of obstetric anal sphincter injuries in subgroups defined by risk factors for OASIS.
Design
Population-based cohort study.
Setting
University hospital setting in Oslo, Norway.
Participants
Two cohorts of all delivering women in the largest hospital in Norway during two time periods (2003–2005 and 2008–2010) were studied. After excluding caesarean sections and preterm deliveries (< week 32), the study population consisted of 31 709 deliveries, among which 907 women were identified with obstetric anal sphincter injury.
Primary and secondary outcome measures
Incidence of OASIS in two time periods. Maternal, obstetrical and foetal risk factors for OASIS were collected from the hospital obstetric database. Univariate analyses and multivariate logistic regression analyses, presenting adjusted ODs for OASIS, were performed.
Results
The OASIS incidence was significantly reduced by 50%, from 4% (591/14787) in the first time period to 1.9% (316/16 922) in the second. This reduction could not be explained by changes in population characteristics or OASIS risk factors during the study years. The reduction of incidence of OASIS between the two study periods was consistent across subgroups of women; regardless of parity, delivery method and infant birth weight.
Conclusions
A marked reduction in the incidence of OASIS was observed in all studied subgroups of women after implementing the training programme for perineal protection. Further, this reduction could not be explained by the differences in patient characteristics across the study period. These findings indicate that the training programme with improved perineal protection markedly reduced the risk of OASIS.
Keywords: Education & Training (see Medical Education & Training), Medical Education & Training, obstetric anal sphincter injury, delivery
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