Levator ani muscle avulsion during childbirth: a risk prediction model
Article first published online: 5 MAR 2014
© 2014 Royal College of Obstetricians and Gynaecologists
BJOG: An International Journal of Obstetrics & Gynaecology
Volume 121, Issue 9, pages 1155–1163, August 2014
How to Cite
Levator ani muscle avulsion during childbirth: a risk prediction model. BJOG 2014;121:1163–1163., , , , .
- Issue published online: 22 JUL 2014
- Article first published online: 5 MAR 2014
- Manuscript Accepted: 28 OCT 2013
- Mayday Childbirth Charity Fund
- levator ani avulsion;
- pelvic organ prolapse;
- risk prediction model;
- transperineal ultrasound
To establish the incidence of levator ani muscle (LAM) avulsion in primiparous women and to develop a clinically applicable risk prediction model.
Observational longitudinal cohort study.
District General University Hospital, United Kingdom.
Nulliparous women at 36 weeks of gestation and 3 months postpartum.
Four-dimensional transperineal ultrasound was performed during both visits. Tomographic ultrasound imaging at maximum contraction was used to diagnose no, minor or major LAM avulsion. A risk model was developed using multivariable ordinal logistic regression.
Main outcome measures
Incidence of LAM avulsion and its risk factors.
Of 269 women with no antenatal LAM avulsion 71% (n = 191) returned postpartum. No LAM avulsion was found after caesarean section (n = 48). Following vaginal delivery the overall incidence of LAM avulsion was 21.0% (n = 30, 95% confidence interval [95% CI] 15.1–28.4). Minor and major LAM avulsion were diagnosed in 4.9% (n = 7, 95% CI 2.2–9.9) and 16.1% (n = 23, 95% CI 10.9–23.0), respectively. Risk factors were obstetric anal sphincter injuries (odds ratio [OR] 4.4, 95% CI 1.6–12.1), prolonged active second stage of labour per hour (OR 2.2, 95% CI 1.4–3.3) and forceps delivery (OR 6.6, 95% CI 2.5–17.2). A risk model and nomogram were developed to estimate a woman's individual risk: three risk factors combined revealed a 75% chance of LAM avulsion.
Twenty-one percent of women sustain LAM avulsion during their first vaginal delivery. Our risk model and nomogram are novel tools to estimate individual chances of LAM avulsion. We can now target postnatal women at risk of sustaining a LAM avulsion.