Objective: Approximately 50% women who give birth after Obstetric Anal Sphincter Injury (OASI) develop anal incontinence (AI) over their lifetime. We review current evidence for protective benefit of planned cesarean section (CS) to prevent AI after OASI. Design and setting: Systematic review and meta-analysis according to prospectively published methodology. Population and methods: All studies reporting outcomes after an OASI and subsequent birth by any mode. Main outcome measures: AI measurement after OASI and subsequent birth. Total AI, new/worsening AI, quality of life, satisfaction, regret. Results: 86 of 2472 screened studies met inclusion criteria. All studies contributing to meta-analyses were at high risk of bias. There was no evidence of difference in new or worsening AI after subsequent vaginal birth (VB) compared to subsequent CS after OASI across all time periods (p=0.53: CI 0.72-1.19; 9 studies, 2104 participants); ≤2y (p=0.83: CI 0.65-1.72; 7 studies, 569 participants) or ≥5y after subsequent birth (p=0.39: CI 0.65-1.18; 2 studies; 1535 participants). There was no difference between subsequent CS or VB in asymptomatic women or for other AI or QOL outcomes. There was no evidence of difference in AI in women who subsequently delivered vs those who did not (p=0.9: CI 0.71-1.34; 10 studies, 970 participants); or pre- subsequent birth vs post-subsequent birth (p=0.31; CI 0.51-1.25, 13 studies, 5496 participants). Conclusions: Due to evidence quality (majority non-randomised studies) we are unable to determine whether planned cesarean is protective against AI after OASI. Higher quality data is required to guide practice in this area, specifically in asymptomatic women and for long-term outcomes.