Is obstetric anal sphincter injury a risk factor for levator ani muscle avulsion in vaginal delivery?

• Published in: Ultrasound in obstetrics & gynecology Vol. 49; no. 2; pp. 257 - 262
• Main Authors: González, M. Simó, Garriga, J. Cassadó, Capel, C. Dosouto, Roda, O. Porta, Capó, J. Perelló, Saladich, I. Gich
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.02.2017; Wiley Subscription Services, Inc
• Subjects: Adult; Anal Canal - injuries; anal sphincter; Delivery, Obstetric - methods; Female; Humans; levator ani muscle; levator ani muscle avulsion; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - injuries; Observer Variation; obstetric anal sphincter injury; Pelvic Floor - injuries; Pregnancy; Prospective Studies; Risk Factors; Tertiary Care Centers; Ultrasonography - methods; vaginal delivery; risk factors; anal sphincter; vaginal delivery; levator ani muscle avulsion; levator ani muscle; obstetric anal sphincter injury
• ISSN: 0960-7692; 1469-0705
• DOI: 10.1002/uog.15847

ABSTRACT Objective To analyze whether women who sustain obstetric anal sphincter injury (OASI) in their first vaginal delivery have a higher incidence of levator ani muscle (LAM) avulsion than do women without OASI. Methods We conducted a prospective observational cohort study of 80 primiparous women who gave birth at our tertiary obstetric unit between September 2011 and July 2013. The women were divided into two groups: women diagnosed with OASI during vaginal delivery (n = 40) and women without OASI (n = 40), matched by mode of delivery and newborn birth weight. Four‐dimensional (4D) transperineal ultrasound was performed in all participants at 6–12 months after delivery to assess for integrity or avulsion of the LAM. Ultrasound images were evaluated by two observers who were blinded to group assignment and clinical data. Interobserver agreement was assessed to determine the reproducibility of 4D transperineal ultrasound for diagnosing LAM avulsion. Results We found no statistically significant differences between the two groups. The incidence of LAM avulsion was 24.3% in the OASI group and 34.2% in the control group (P = 0.448). Interobserver agreement in the diagnosis of LAM avulsion in the study population using 4D transperineal ultrasound was 89.5%, with a kappa index of 0.76. Conclusions Our findings do not support OASI as a risk factor for LAM avulsion. Prospective studies in larger populations are needed to establish the biomechanical relationships of the pelvic floor structures involved in vaginal delivery. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.