Obstetric Anal Sphincter Injuries: Risk Factors, Pelvic Floor Dysfunction, and Quality of Life Outcomes

<i>Background and Objectives</i>: Obstetric anal sphincter injuries (OASISs) are severe complications of vaginal delivery that can result in long-term pelvic floor dysfunction and reduced quality of life. Global data indicate a rising incidence of OASISs, including in Lithuania. This study aimed to identify risk factors for OASISs and evaluate their impact on urinary (UI) and fecal incontinence (FI), pelvic organ prolapse (POP), and quality of life in affected women. <i>Materials and Methods</i>: A retrospective case-control study was conducted at the Lithuanian University of Health Sciences Hospital (LUHS) Kauno Klinikos in 2024. Women who gave birth between 2004 and 2023 and experienced OASIS (<i>n</i> = 90) were compared with women matched for birth history but without perineal tears (<i>n</i> = 90). Data were collected from medical records and electronic questionnaires, including the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF), Wexner score, Pelvic Organ Prolapse Symptom Score (POP-SS), and Pelvic Floor Impact Questionnaire (PFIQ-7). Participants were grouped by delivery year (2004-2013 or 2014-2023). Statistical analysis was performed using Mann-Whitney U, Chi-square, Fisher's exact and Student's <i>t</i>-tests, with <i>p</i> < 0.05 considered significant. <i>Results</i>: Newborn weight and vacuum-assisted delivery were significantly associated with OASIS (<i>p</i> < 0.05 and <i>p</i> = 0.029). In the 2014-2023 cohort, women with OASIS reported significantly higher rates and severity of UI, FI, and POP symptoms compared to controls. Quality of life scores related to UI and FI were significantly worse in the recent OASIS group, whereas no significant differences were observed in the 2004-2013 cohort. <i>Conclusions</i>: Between 2004 and 2023, 0.4% of women who gave birth at LUHS experienced third- or fourth-degree perineal tears, with newborn weight and vacuum extraction identified as risk factors. These women reported higher rates of UI and FI and POP, and those who delivered between 2014 and 2023 rated their related quality of life significantly worse than women without OASIS.