Parity and anal sphincter trauma
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Introduction and hypothesis
Obstetric anal sphincter injury (OASI) is a form of maternal trauma secondary to vaginal birth. Women with a history of OASI are deemed to be at a higher risk of recurrence. However, it is unclear if multiparity is associated with higher prevalence. The aim of the study was to test the following hypothesis: the prevalence of external anal sphincter (EAS) tears diagnosed on transperineal ultrasound (TPUS) is related to vaginal parity.
A retrospective observational study on 1,273 women who attended a tertiary urogynecology service between January 2014 and December 2016. Patients had undergone a standardized interview, clinical examination and 4D TPUS. Tomographic ultrasound imaging was used to evaluate the EAS, blinded to all clinical data.
Of 1,273 women, 1,143 (90%) were vaginally parous, with a mean vaginal parity of 2 (range 1–8). Mean age was 54 (range 17–89) years. Anal incontinence was reported in 186 women (15%) with an average St Mark’s incontinence score of 12 (range 1–23). EAS defects on ultrasound were identified in 148 (12%). On univariate analysis, there was no significant difference in the prevalence of EAS defects in vaginally primiparous and multiparous women (p = 0.460).
There is no significant difference in the prevalence of EAS tears between vaginally primiparous and multiparous women. This argues against additional traumatic effects of subsequent vaginal births.
KeywordsAnal sphincter trauma Anal incontinence Maternal trauma Parity Tomographic ultrasound imaging Transperineal ultrasound
Compliance with ethical standards
Conflicts of interest
KL Shek and HP Dietz have received unrestricted educational grants from GE Medical. The other authors have no conflicts of interest to declare.