Peer-reviewed article
Incidence and Risk Factors of Obstetric Anal Sphincter Injury at a Tertiary Care Hospital in Thailand: A 10-Year Retrospective Cohort Study.
Unpikool U, Jongjakapun A, Temtanakitpaisan T, Chongsomchai C ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This is a medical study examining obstetric anal sphincter injuries (OASI) in women during vaginal delivery at a Thai hospital over 10 years. The research found that 9.4% of vaginal deliveries resulted in OASI, with risk factors including forceps use, prolonged labor, and labor augmentation. The study notes that injury rates declined when episiotomy (surgical cutting) rates decreased.
Key points
- Overall OASI incidence was 9.4% among 9,956 vaginal deliveries, with most cases being third-degree injuries (8.7%)
- OASI incidence declined from 9.8% to 6.1% over the decade, correlating with reduced episiotomy rates
- Forceps extraction was the strongest risk factor (6.15 times increased odds)
- Delivery without episiotomy was protective, reducing OASI risk by 59%
- Other risk factors included prolonged second stage of labor, labor augmentation, and higher neonatal birthweight
Limitations
This study focuses on maternal health outcomes during childbirth rather than child well-being, and does not measure impacts on the newborn or long-term child health outcomes. The retrospective design cannot establish causation, only associations between delivery practices and maternal injury.
Abstract
Introduction and hypothesis Obstetric anal sphincter injury (OASI) is a severe complication of vaginal delivery leading to short- and long-term consequences affecting women's physical and psychological health. This study is aimed at evaluating the incidence and risk factors of OASI at a tertiary care centre over the past decade. Methods This retrospective cohort study included all singleton primiparous and multiparous women who delivered vaginally between 2014 and 2023. Women giving birth at < 24 weeks and whose child weighed < 500 g at birth, or with incomplete records, were excluded. Key maternal and obstetric factors were extracted and analysed using univariate and multivariate logistic regression. Results Among 9956 women, the overall incidence of OASI was 9.4% (third-degree 8.7% and fourth-degree 0.7%). The incidence of OASI declined from 9.8% to 6.1% in the past decade, coinciding with a reduction in episiotomy rates. Multivariate analysis identified forceps extraction (aOR 6.15, 95% CI 3.66-10.33), prolonged second stage of labour (aOR 2.47, 95% CI 2.00-3.05), labour augmentation (aOR 1.62, 95% CI 1.38-1.89), deliveries performed by a faculty member (aOR 1.25, 95% CI 1.03-1.51) and every 100-g increase in neonatal birthweight (aOR 1.09, 95% CI 1.08-1.11) as significant risk factors. Delivery without an episiotomy was a protective factor (aOR 0.41, 95% CI 0.30-0.56). Conclusions The high incidence of OASI at our institution highlights the impact of obstetric practices. The findings reinforce the need for restrictive episiotomy policies and targeted strategies to mitigate modifiable risk factors associated with OASI.