Ultrasound evaluation of the Cesarean scar: relation between a niche and postmenstrual spotting

To evaluate the relationship between a niche and abnormal uterine bleeding, and to develop a sonographic classification of niches and evaluate its relationship to abnormal uterine bleeding.

An observational prospective cohort study was performed between October 2007 and May 2009. All women who had a Cesarean section performed in our hospital were asked to participate. Two hundred and twenty-five women were included and examined with both transvaginal sonography (TVS) and gel instillation sonohysterography (GIS) 6-12 months after the Cesarean section. In case of a niche, the depth, volume and residual myometrium were measured, and the shape was assessed according to a specified classification. A questionnaire and pictorial blood loss assessment chart were filled in.

The prevalence of a niche on evaluation with TVS and GIS was 24.0% and 56.0%, respectively. A niche was considered to be present if the depth was at least 1 mm visualized with GIS. Postmenstrual spotting was reported by 33.6% of women with a niche and 15.2% of women without a niche (P = 0.002). The niche volume was significantly different between women with and without postmenstrual spotting (P = 0.02). Most niches had a semicircular (50.4%) or triangular shape (31.6%). No significant relationship was identified between the shape of the niche and postmenstrual spotting (P = 0.19).

A niche is present in 56.0% of women with a history of Cesarean section when examined by GIS and is associated with postmenstrual spotting. Semicircular and triangular niches are most common, but the shape is not related to postmenstrual spotting.