Objective: Summary of the mutual relationship between vaginal delivery and anal incontinence. Design: Retrospective case-control study. Setting: Department of Gynaecology and Obstetrics, Charles University and Faculty Hospital Pilsen, Czech Republic. Methods: 9600 vaginal deliveries between January 1997 and March 2004 were evaluated. The aim of the study was to observe the incidence of the 3rd degree tear and identification of the risk factors. The recognition of the perineal injury was open to the individual interpretation and assessment of the doctors involved. Results: The incidence of the 3rd degree tear was 0.84%. The diagnostics of the 3rd degree tear was significantly more frequent if the evaluation of the perineal injury was performed by the urogynaecologists (p<0.001). Statistically significant risk factors of the 3rd degree tear in the univariate and multivariate analysis were: forceps, shoulder dystocia, the length of the 2nd stage of labour and maternal cooperation at the final phase of delivery. Parturity (primiparity), birth weight and episiotomy (when all types of episiotomy were included) were statistically significant only in the univariate analysis. Mediolateral episiotomy was not proved to be either the risk or the protective significant factor. Summary: The diagnostics of the 3rd degree tear demands a detailed knowledge of the structure and anatomy of the pelvic floor. Asufficient amount of experience and erudition are the requirements for the prevention, diagnostics and subsequent treatment of this injury.

        Key words: third degree tear, perineal trauma, delivery, forceps, episiotomy, maternal cooperation