Isthmocele risk in repeated cesarean: the diagnostic and clinical role of morphometric parameters

This study aimed to evaluate the impact of repeated cesarean deliveries on isthmocele formation and to investigate the diagnostic value and clinical presentation of morphometric parameters, including niche depth, width, length, residual myometrial thickness (RMT), adjacent myometrial thickness (AMT), and the depth/AMT ratio.

A cross-sectional study was conducted with 116 symptomatic and asymptomatic women aged 18-45 years who had undergone one or more cesarean sections. The presence and dimensions of the isthmocele were assessed via transvaginal ultrasonography using Delphi consensus criteria. Morphometric and obstetric data were analyzed using descriptive statistics, correlation analysis, and binary logistic regression.

Isthmocele was identified in 71.6% of participants, with prevalence rising from 42.9% after the first cesarean to 100% after the fourth. The isthmocele group had significantly higher gravidity, parity, and cesarean numbers (p < 0.001). Niche depth, length, and the depth/AMT ratio were significantly elevated, while RMT was reduced (p < 0.001). The number of cesareans showed a strong negative correlation with RMT (r = -0.499, p < 0.001) and a strong positive correlation with the depth/RMT ratio (r = 0.615, p < 0.001). Multivariate analysis identified having three or more cesareans as an independent predictor of isthmocele (OR = 15.6; 95% CI 3.27-74.4; p < 0.001). Niche length had the highest diagnostic accuracy for symptomatic isthmocele (AUC 0.700; 95% CI 0.589-0.796; cutoff 5 mm).

Repeated cesarean deliveries significantly increase both the risk and severity of isthmocele. In women with four cesareans, isthmocele was detected in 100% of cases. A niche length of ≥ 5 mm proved to be the most reliable morphometric marker in identifying symptomatic cases.

These findings emphasize the importance of routine transvaginal ultrasound screening post-cesarean-especially in women with multiple cesarean sections-and the incorporation of morphometric assessment (including RMT and depth/RMT ratio) into clinical decision-making.