PhD research: Subsequent birth after obstetric anal sphincter injury

By Sara Webb on 25 May 2018 Midwives Magazine Research OASI - Obstetric anal sphincter injuries

A specialist perineal midwife on her doctoral study.

Background

An estimated 60% to 70% of women undergoing a vaginal birth will sustain perineal trauma that requires suturing. Obstetric anal sphincter injuries (OASIS) are reported to occur in 0.6% to 9% of vaginal deliveries and are a major risk factor of anal incontinence in childbearing women.

Aim

To investigate the impact of a subsequent birth and its mode on bowel function and quality of life (QoL) in women with a previous OASIS.

Methodology

The research consisted of three linked studies. The first was a systematic review and meta-analysis of the available published literature regarding the impact of mode of subsequent birth on bowel symptoms and/or QoL for women with previous OASIS. The second was a postal questionnaire-based follow-up study of 294 women who had previously attended an OASIS clinic to assess longer-term bowel function and QoL. The third was a prospective cohort study of 175 women with previous OASIS reviewed prior to and following the subsequent birth.

Findings

Due to the poor methodological quality and overall heterogeneity of the reviewed studies, it was not possible to determine the optimal mode of subsequent births for women with previous OASIS and therefore better data was needed. In the absence of higher-quality evidence, the review and meta-analysis would support the current recommendation of a subsequent vaginal birth for women with previous OASIS who demonstrate no bowel symptoms or sphincter defects.

The follow-up study and the prospective cohort study both added considerably to the limited data. First, both of these studies demonstrated the relationship of short-term bowel symptoms and identification of maternal, neonatal and birth-related characteristics that are predictors of longer-term outcomes. They also highlight the importance of specialist review, both postnatally following OASIS and antenatally prior to a subsequent birth, to accurately record the presence of any bowel symptoms.

Second, through our cohort study that satisfied all the methodological and quality standards found lacking in currently available studies, for women with previous OASIS who have no bowel symptoms and/or known defects in the anal sphincter muscle, a decision to pursue a subsequent vaginal birth appears sensible.

Implications

These studies provide reassurance for clinicians to support, and for women with a previous OASIS who have normal bowel function and have no anal sphincter abnormalities to pursue, a subsequent vaginal birth.

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Dr Sara Webb is a specialist perineal midwife and research fellow at Birmingham Women’s and Children’s NHS Foundation Trust and the University of Birmingham