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.