Long‐term complications of caesarean section. The niche in the scar: a prospective cohort study on niche prevalence and its relation to abnormal uterine bleeding

<jats:sec><jats:title>Objective</jats:title><jats:p>To study the prevalence of niches in the caesarean scar in a random population, and the relationship with postmenstrual spotting and urinary incontinence.</jats:p></jats:sec><jats:sec><jats:title>Design</jats:title><jats:p>A prospective cohort study.</jats:p></jats:sec><jats:sec><jats:title>Setting</jats:title><jats:p>A teaching hospital in the Netherlands.</jats:p></jats:sec><jats:sec><jats:title>Population</jats:title><jats:p>Non‐pregnant women delivered by caesarean section.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Transvaginal ultrasound (<jats:styled-content style="fixed-case">TVU</jats:styled-content>) and gel instillation sonohysterography (<jats:styled-content style="fixed-case">GIS</jats:styled-content>) were performed 6–12 weeks after caesarean section. Women were followed by questionnaire and menstruation score chart at 6–12 weeks, 6 months, and 12 months after caesarean section.</jats:p></jats:sec><jats:sec><jats:title>Main outcome measures</jats:title><jats:p>Prevalence of a niche 6–12 weeks after caesarean section, using <jats:styled-content style="fixed-case">TVU</jats:styled-content> and <jats:styled-content style="fixed-case">GIS</jats:styled-content>. Secondary outcomes: relation to postmenstrual spotting and urinary incontinence 6 and 12 months after caesarean section; and niche characteristics, evaluated by <jats:styled-content style="fixed-case">TVU</jats:styled-content> and <jats:styled-content style="fixed-case">GIS</jats:styled-content>.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Two hundred and sixty‐three women were included. Niche prevalence was 49.6% on evaluation with <jats:styled-content style="fixed-case">TVU</jats:styled-content> and 64.5% with <jats:styled-content style="fixed-case">GIS</jats:styled-content>. Women with a niche measured by <jats:styled-content style="fixed-case">GIS</jats:styled-content> reported more postmenstrual spotting than women without a niche (<jats:styled-content style="fixed-case">OR</jats:styled-content> 5.48, 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 1.14–26.48). Women with residual myometrium at the site of the uterine scar measuring <50% of the adjacent myometrial thickness had postmenstrual spotting more often than women with a residual myometrial thickness of >50% of the adjacent myometrial thickness (<jats:styled-content style="fixed-case">OR</jats:styled-content> 6.13, 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 1.74–21.63). Urinary incontinence was not related to the presence of a niche.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>A niche is present in 64.5% of women 6–12 weeks after caesarean section, when examined by <jats:styled-content style="fixed-case">GIS</jats:styled-content>. Postmenstrual spotting is more prevalent in women with a niche and in women with a residual myometrial thickness of <50% of the adjacent myometrium.</jats:p></jats:sec>