Incidence of Obstetric Anal Sphincter Injuries After Training to Protect the Perineum

Guideline No. 457: Obstetrical Anal Sphincter Injuries (OASIS) Part I: Prevention, Recognition, and Immediate Management

OBJECTIVE

The purpose of this guideline is to promote recognition and preventive strategies for obstetrical anal sphincter injuries. Furthermore, it provides guidance on primary repair and immediate postpartum management for obstetrical anal sphincter tears in order to minimize further negative sequelae.

TARGET POPULATION

All patients having a vaginal delivery and those who have sustained an obstetrical anal sphincter injury.

OUTCOMES

Certain preventive strategies have been associated with lower rates of obstetrical anal sphincter injuries (e.g., fetal head flexion and control, appropriate use of mediolateral episiotomy). Management strategies, including appropriate diagnosis and repair of obstetrical anal sphincter injuries, antibiotic prophylaxis, and bowel and bladder function management can decrease associated short- and long-term complications.

BENEFITS, HARMS, AND COSTS

Implementation of the recommendations in this guideline may increase detection, prevention, and appropriate management of obstetrical anal injuries, thus limiting the future burden associated with these injuries. Implementation of the recommended classification of obstetrical anal sphincter injuries will improve national and international research efforts.

EVIDENCE

Published literature was retrieved through searches of PubMed, Ovid, Medline, Embase, Scopus, and the Cochrane Library from September 1, 2014, through November 30, 2023, using appropriate MeSH terms (delivery, obstetrics, obstetric surgical procedures, obstetric labor complications, anal canal, episiotomy) and keywords (OASIS, obstetrical anal sphincter injury, anal injury, anal sphincter, vaginal delivery, suture, fecal incontinence, anal incontinence, overlap repair, end-to-end repair, bladder protocol, analgesia). Results were restricted to systematic reviews, meta-analyses, randomized controlled trials/controlled clinical trials, observational studies, and clinical practice guidelines. Results were limited to English- or French-language materials. Evidence was supplemented with references from the 2015 Society of Obstetricians and Gynaecologists of Canada guideline no. 330.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional recommendations).

INTENDED AUDIENCE

Obstetrical care providers.

TWEETABLE ABSTRACT

Updated Canadian guideline on recognition, prevention and management of obstetrical anal sphincter injuries (OASIS).

SUMMARY STATEMENTS

RECOMMENDATIONS.

A pre-post implementation study of a care bundle to reduce perineal trauma in unassisted births conducted by midwives

PROBLEM

The perineal-bundle is a complex intervention widely implemented in Australian maternity care facilities.

BACKGROUND

Most bundle components have limited or conflicting evidence and the implementation required many midwives to change their usual practice for preventing perineal trauma.

AIM

To measure the effect of perineal bundle implementation on perineal injury for women having unassisted births with midwives.

METHODS

A retrospective pre-post implementation study design to determine rates of second degree, severe perineal trauma, and episiotomy. Women who had an unassisted, singleton, cephalic vaginal birth at term between two time periods: January 2011 - November 2017 and August 2018 - August 2020 with a midwife or midwifery student accoucheur. We conducted logistic regression on the primary outcomes to control for confounding variables.

FINDINGS

data from 20,155 births (pre-implementation) and 6273 (post-implementation) were analysed. After implementation, no significant difference in likelihood of severe perineal trauma was demonstrated (aOR 0.86, 95% CI 0.71-1.04, p = 0.124). Nulliparous women were more likely to receive an episiotomy (aOR 1.49 95% CI 1.31-1.70 p < 0.001) and multiparous women to suffer a second degree tear (aOR 1.18 95% CI 1.09-1.27 p < 0.001).

DISCUSSION

This study adds to the growing body of literature which suggests a number of bundle components are ineffective, and some potentially harmful. Why, and how, the bundle was introduced at scale without a research framework to test efficacy and safety is a key concern.

CONCLUSION

Suitably designed trials should be undertaken on all proposed individual or grouped perineal protection strategies prior to broad adoption.

Posterior compartment symptoms in primiparous women 1 year after non-assisted vaginal deliveries: a Swedish cohort study

Introduction and hypothesis

This is a prospective cohort follow-up study based on the hypothesis that primiparous women with non-assisted vaginal deliveries and a second-degree perineal tear have more posterior compartment symptoms 1 year after delivery than those with no or first-degree tears.

Methods

A follow-up questionnaire, including validated questions on pelvic floor dysfunction, was completed 1 year postpartum by 410 healthy primiparas, delivered without instrumental assistance at two maternity wards in Stockholm between 2013 and 2015. Main outcome measures were posterior compartment symptoms in women with second-degree perineal tears compared with women with no or only minor tears.

Results

Of 410 women, 20.9% had no or only minor tears, 75.4% had a second-degree tear, and 3.7% had a more severe tear. Of women presenting with second-degree tears, 18.9% had bowel-emptying difficulties compared with 20.0% of women with minor tears. Furthermore, almost 3% of them with second-degree tears complained of faecal incontinence (FI) of formed stool, 7.2% of FI of loose stool compared with 1.2% and 3.5% respectively in women with no or only minor tears.

Conclusions

Symptomatic pelvic floor dysfunction is common among primiparous women within 1 year following uncomplicated vaginal delivery, and there are no significant differences between second-degree perineal tears and minor tears. These symptoms should be addressed in all women after delivery to improve pelvic floor dysfunction and quality of life.

Impact of a quality improvement project to reduce the rate of obstetric anal sphincter injury: a multicentre study with a stepped-wedge design

Objective

To evaluate the impact of a care bundle (antenatal information to women, manual perineal protection and mediolateral episiotomy when indicated) on obstetric anal sphincter injury (OASI) rates.

Design

Multicentre stepped‐wedge cluster design.

Setting

Sixteen maternity units located in four regions across England, Scotland and Wales.

Population

Women with singleton live births between October 2016 and March 2018.

Methods

Stepwise region by region roll‐out every 3 months starting January 2017. The four maternity units in a region started at the same time. Multi‐level logistic regression was used to estimate the impact of the care bundle, adjusting for time trend and case‐mix factors (age, ethnicity, body mass index, parity, birthweight and mode of birth).

Main outcome measures

Obstetric anal sphincter injury in singleton live vaginal births.

Results

A total of 55 060 singleton live vaginal births were included (79% spontaneous and 21% operative). Median maternal age was 30 years (interquartile range 26–34 years) and 46% of women were primiparous. The OASI rate decreased from 3.3% before to 3.0% after care bundle implementation (adjusted odds ratio 0.80, 95% CI 0.65–0.98, P = 0.03). There was no evidence that the effect of the care bundle differed according to parity (P = 0.77) or mode of birth (P = 0.31). There were no significant changes in caesarean section (P = 0.19) or episiotomy rates (P = 0.16) during the study period.

Conclusions

The implementation of this care bundle reduced OASI rates without affecting caesarean section rates or episiotomy use. These findings demonstrate its potential for reducing perineal trauma during childbirth.

Tweetable abstract

OASI Care Bundle reduced severe perineal tear rates without affecting caesarean section rates or episiotomy use.

OASI Care Bundle reduced severe perineal tear rates without affecting caesarean section rates or episiotomy use.