The association between uterine scar defect (niche) and the presence of symptoms

Research question: Is there association between the presence of a uterine niche and the presence of symptoms? Design: This cross-sectional study was conducted at a single tertiary medical centre. All women who underwent Caesarean section from January 2017 to June 2020 were invited to the gynaecological clinics, and requested to complete a questionnaire regarding symptoms related to the presence of a niche (heavy menstrual bleeding, intermenstrual spotting, pelvic pain, infertility). Transvaginal two-dimensional ultrasonography was performed to assess the uterus and uterine scar characteristics. The primary outcome was defined as the presence of a uterine niche, evaluated by length, depth, residual myometrial thickness (RMT) and ratio between the residual myometrial thickness (RMT) and adjacent myometrial thickness (AMT). Results: Of 524 women who were eligible and scheduled for evaluation, 282 (54%) completed the follow-up; 173 (61.3%) were symptomatic and 109 (38.6%) asymptomatic. Niche measurements, including RMT/AMT ratio, were comparable between the groups. In a sub-analysis of each symptom, heavy menstrual bleeding and intermenstrual spotting were associated with reduced RMT (P = 0.02 and P = 0.04, respectively) compared with women with normal menstrual bleeding. An RMT less than 2.5 mm was significantly more prevalent in women reporting heavy menstrual bleeding (11 [25.6%] versus 27 [11.3%]; P = 0.01] and new infertility (7 [16.3%] versus 6 [2.5%]; P = 0.001]. In logistic regression analysis, infertility was the only symptom associated with an RMT less than 2.5 mm (B = 1.9; P = 0.002). Conclusions: A reduced RMT was found to be associated with heavy menstrual bleeding and intermenstrual spotting, while values below 2.5 mm were also associated with infertility.