Objective: To review risk factors for obstetric anal sphincter rupture (OASR) and possible preventive strategies as well as clinical outcomes by means of a selected literature review. Material and Methods: I have based my work primarily on articles recommended by my supervisor Professor Anne Cathrine Staff and by her PhD student, lecturer and senior consultant Katariina Laine. I supplemented with some clinical guidelines, reviews and studies identified by a search of the PubMed database. Search terms included obstetric anal sphincter rupture, obstetric anal sphincter injury, obstetric labor complications, perineum, birth, perineal laceration, birth position, water birth, anal incontinence, hands poised, episiotomy. Additional sources are textbooks and a medical dictionary.
Results: Main risk factors for OASR that are well documented are first vaginal birth, birth weight and vaginal operational delivery. Risk factors with some impact are maternal age, gestational age, prolonged second stage of labor, occipito-posterior presentation, high BMI as well as median episiotomy. Further discussed risk factors are: epidural anesthesia, induction of labor and ethnicity. Obstetric techniques with protective effect include the use of vacuum assisted delivery rather than forceps in operational vaginal deliveries, episiotomy only on indication, episiotomy cut with a rather large angle from the midline, manual protection of the perineum during fetal head crowning and well trained accoucheurs. OASR is a strong risk factor for anal incontinence. As many as 30% to 60% of women with diagnosed and repaired OASR at delivery experience symptoms of anal incontinence in long term follow-up. Additional comorbidities with OASR are urinary incontinence, pelvic floor prolapse symptoms, sexual dysfunction and reduced health-related quality of life.
Conclusions: Obstetric anal sphincter rupture is a complication of vaginal delivery that affects many women due to many vaginal births worldwide. A considerable share of affected patients experience long term health related consequences. Low frequencies of OASR can be achieved by optimizing obstetrical techniques.