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To study the prevalence of niches in the caesarean scar in a random population, and the relationship with postmenstrual spotting and urinary incontinence.
A prospective cohort study.
A teaching hospital in the Netherlands.
Non-pregnant women delivered by caesarean section.
Transvaginal ultrasound (TVU) and gel instillation sonohysterography (GIS) 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.
Main outcome measures
Prevalence of a niche 6–12 weeks after caesarean section, using TVU and GIS. Secondary outcomes: relation to postmenstrual spotting and urinary incontinence 6 and 12 months after caesarean section; and niche characteristics, evaluated by TVU and GIS.
Two hundred and sixty-three women were included. Niche prevalence was 49.6% on evaluation with TVU and 64.5% with GIS. Women with a niche measured by GIS reported more postmenstrual spotting than women without a niche (OR 5.48, 95% CI 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 (OR 6.13, 95% CI 1.74–21.63). Urinary incontinence was not related to the presence of a niche.
A niche is present in 64.5% of women 6–12 weeks after caesarean section, when examined by GIS. Postmenstrual spotting is more prevalent in women with a niche and in women with a residual myometrial thickness of <50% of the adjacent myometrium.