Association of Obstetric anal Sphincter injuries (OASIS) with duration of Second Stage of Labor

Abstract

Background: Obstetric anal sphincter injuries (OASIS) are a serious issue in contemporary obstetrics that can lead to negative repercussions on the health of women. These types of injuries including 3rd and 4th degree perineal tears, which involve the muscles around the anal sphincter and may also extend to the rectal mucosa. We investigated the correlation of long duration of second-stage of labor and occurrence of OASIS in women delivering at Ayub Teaching Hospital, Abbottabad.

Methodology: The study was a cross-sectional, observational study conducted at the authors' tertiary care center and included 105 women with full-term singleton pregnancies with diagnosis of prolonged second stage. Maternal demographics, obstetric history, labor characteristics, mode of delivery, perineal trauma and postpartum symptoms were collected. Second-stage labor duration: was dichotomized based on standard clinical definition. Data were summarized using descriptive statistics, and we conducted comparative analyses (Chi-square tests/t-tests) to examine the relationship between second-stage labor duration, assisted deliveries, episiotomy use and OASIS incidence with p ≤0.05 considered significant.

Results: The prevalence of OASIS was 12.4% (n=13). Women with OASIS had a significantly longer mean second-stage labor duration (256.9 vs. 212.7 minutes, p<0.001). Mode of delivery was a key factor, with 69 (65.7%) of OASIS cases occurring in spontaneous vaginal deliveries and 24 (22.9%) in assisted deliveries. Episiotomy did not significantly reduce OASIS risk (p=0.973). Postpartum symptoms, including fecal incontinence (15.4%) and urinary incontinence (30.8%), were more common in women with OASIS.

Conclusion: Prolonged second-stage labor is a significant risk factor for OASIS, necessitating early intervention, perineal protection, and optimized labor management. Given the high postpartum morbidity, routine screening and pelvic floor rehabilitation should be integrated into postpartum care. Future research should focus on preventive strategies and long-term maternal outcomes.

Keywords: Obstetric anal sphincter injuries, prolonged second-stage labor, perineal trauma, episiotomy, assisted vaginal delivery, postpartum incontinence.