An evaluation of the risk factors associated With sustaining perineal trauma At childbirth, subsequent birthing outcomes and the effects on pelvic floor dysfunction

Abstract

More than 85% of women sustain some form of perineal trauma during vaginal childbirth in the United Kingdom (UK), which equates to approximately 350,000 injuries a year. Obstetric anal sphincter injuries (OASIs), the most severe form of perineal laceration, are sustained in 2.9% of vaginal births and are a recognised major risk factor for long-term anal incontinence and faecal urgency. Careful consideration needs to be made regarding subsequent delivery after an OASI due to the risk of recurrence and the resultant potential for deterioration in symptoms of pelvic floor dysfunction.

The purpose of this research was to evaluate the risk factors associated with OASIs; to explore the birthing outcomes at subsequent delivery after sustaining an OASI and to delineate what influenced the risk of a recurrent injury. This was achieved through retrospective analysis of prospectively collected data in both single- and multi-centre settings. The symptomatic and personal effects of sustaining an injury on symptoms of pelvic floor dysfunction were evaluated through quantitative analysis of data and free text comments provided by means of a postal questionnaire.

This thesis demonstrated that OASIs were more likely with increased maternal age, in those of Asian ethnicity, after a prolonged pushing stage of labour, if the delivery was post-term and if the infant weighed more than four kilograms. Those delivering vaginally after a previous Caesarean section (CS) were at greater risk of an OASI than the primiparous population; even more so if the CS was an emergency. The risk of recurrent OASI (rOASI) was also greater than the primiparous risk, further predisposing women to symptoms of anal sphincter dysfunction. Increased maternal age, high offspring birth weight, and more severe grade of OASI were positive predictors for rOASI. Mediolateral episiotomy was protective against rOASI. Additionally, this thesis also showed the most important indicator for long-term symptoms of PFD following an OASI, regardless of subsequent deliveries and the mode of the subsequent deliveries, was the initial OASI.

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ORCID for John Primrose: orcid.org/0000-0002-2069-7605

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