Outcomes for obstetric anal sphincter injuries and anal incontinence following introduction of a perineal bundle

Introduction:

In Australia a national improvement program was implemented in 2018, with the aim to reduce obstetric anal sphincter injuries (OASI) by 20% through introduction of a perineal protection bundle (PPB). This involved warm compresses in the second stage, a controlled hands-on birth, a specific technique for episiotomy, routine rectal examination and grading of perineal tears by two experienced clinicians. This study reviews the effect at one site by outlining the impact on OASI rates and anal incontinence in first vaginal births.

Methods:

Retrospective deidentified data was extracted to compare women’s outcomes before, during and after implementation. The PPB was implemented as standard of care for all vaginal births, with each element being recommended to care providers and consent obtained by clinicians for each woman. For analysis we included all women who had their first vaginal birth from 2016–June 2023. A statistical analysis compared the periods prior to use (2016–17, 1830 women), when it was implemented (2018, 784 women), and following (2019–2023, 3581 women). All women who sustained OASI were offered review in at 6 weeks and 6 months, where a St Mark’s Incontinence Score was obtained. Rates of OASI, caesarean at full dilatation, episiotomies and anal incontinence rates where OASI was sustained were compared using the odds ratio chi-square test.

Results:

A 40% reduction (3.3% absolute reduction from 8.3% to 5.0%) in OASI was noted. There was an increase in the episiotomy rate from 48% to 56% (OR 1.37), however this was mostly for vacuums, with no evidence for a significant increase in normal vaginal births. There was no change in caesarean sections at full dilatation (3%). There was no significant difference in anal incontinence before, during or after, with St Mark’s Incontinence Scores of $\ge$ 6 in 6.4%–11.3% at 6 weeks, and 3.5%–5% at 6 months.

Conclusion:

The study identified a reduction in OASI however no reduction in anal incontinence. This provides support for use of the PPB. This study is limited in that we were only able to review outcomes from a single site, with implementation of multiple changes in practice simultaneously.