The safety of vaginal delivery following obstetric anal sphincter injury- A retrospective pilot study using transperineal ultrasound algorithm

Objective: The optimal mode of subsequent delivery following obstetric anal sphincter injury (OASI) is arguable. This pilot study assessed the impact of using our suggested transperineal ultrasound (TPUS) based algorithm on recurrent OASI and cesarean deliveries (CD) rates, as well as anal incontinence, in a subsequent delivery. Methods: This retrospective observational study included women following OASI who sought consultation regarding the safety of a subsequent vaginal delivery (VD). The study group included women who underwent a comprehensive evaluation in a dedicated postpartum perineal clinic established in 2020. Their evaluation encompassed symptom assessment, physical examination, and a four-dimensional TPUS scan. A recommendation regarding the future mode of delivery was given based on a TPUS-based algorithm. The control group received recommendations based on subjective clinical judgment, as their OASI occurred before the clinic’s establishment. Primary outcomes included rates of recurrent OASI and scheduled CD, while secondary outcomes included de novo or worsening anal incontinence. Results: Demographic characteristics were comparable between the study (n = 55) and control (n = 68) groups. The study group had more reassurance to deliver vaginally (70.9% vs. 11.7%, p < 0.001) and their actual subsequent VD rate was higher (53.3% vs. 19.6%, p < 0.001) without an increase in recurrent OASI (0% vs. 10%, p = 0.22). No difference was observed in de novo anal incontinence between those who subsequently delivered vaginally and those who had a CD (20% vs. 16.6%, p = 0.78). Conclusion: Assessing women following obstetric anal sphincter injury using a noninvasive trans-perineal ultrasound-based algorithm is feasible and may reduce the rate of subsequent cesarean delivery without increasing anal incontinence.