Background: Many women who experience anal sphincter tear will suffer from anal incontinence. The most important tool to avoid this is to recognise the obstetric risk factors involved and thereby prevent injury.
Aims: The aim of this study was to analyse and evaluate the risk factors of anal sphincter tear during delivery.
Methods: Of a total of 57,943 vaginal deliveries, we identified 565 women with partial or total rupture of the anal sphincter and compared these women with 565 controls without sphincter tear with respect to possible risk factors.
Results: Several factors were significantly associated with sphincter tears, including nulliparity, birthweight, instrumental delivery, episiotomy, malpresentation, maternal age and epidural analgesia. The importance of these variables was further confirmed in a stepwise logistic regression analysis. Age was found to be a significant risk factor only when the birthweight was less than 4000 g. Episiotomy more than doubled the risk of sphincter tear when delivery was non-instrumental.
Conclusion: There are several independent risk factors that should be considered when making decisions regarding delivery mode. Maternal age and episiotomy in non-instrumental delivery are two of these.