Objective: To investigate the relationship between episiotomy and the occurrence of sphincter injury in births at a Norwegian University Hospital, 2000-2007.
Study design: Prospective epidemiologic study.
Subjects: Our data were registered continuously throughout the period 2000-2007, including a total number of 28078 births, out of which a total number of 20539 satisfied our inclusion criteria (vaginal, singleton deliveries, occiput-anterior presentation, deliveries, no use of vacuum or forceps).
Methods: Sphincter injury was defined to include all perineal tears of 3rd and 4th degree. Minor perineal damages were not included in our database hence not investigated. Our method of analysis was univariate, including calculations of 95 % confidence intervals.
Results: In our database 3011 (14.7 %) episiotomies were performed, separate analysis of nulli- and multiparous women demonstrated that episiotomies were performed significantly more often in nulliparous than multiparous women (3.4 times more often). Sphincter injury occurred at a rate of 3.63 %, varying from 2.11 % (2007) to 5.09 % (2002), with a statistical significant higher (p<0.05) rate in nulliparas (5.78 % versus 2.32 % in multiparas). Further we found that there was a higher rate of sphincter damage where episiotomy was used, especially in the multiparas. The midwives experience seemed not to be correlated with a less frequent use of episiotomy, but a correlation between being experienced and having more sphincter injuries was found.
Conclusion: No protective effect of mediolateral episiotomy on the occurrence of sphincter lacerations was found. For the entire population our study showed a positive correlation between mediolateral episiotomy and sphincter lacerations. Hence the use of episiotomy should only be encouraged on foetal indications.