Magnetic resonance imaging-based classification of cesarean scar pregnancy: prediction of intraoperative blood loss and the role of preoperative uterine artery embolization.

Objectives: To establish a magnetic resonance imaging (MRI)-based classification system for cesarean scar pregnancy (CSP), assess its ability to predict intraoperative blood loss, and evaluate the effectiveness of prophylactic uterine artery embolization (UAE). Methods: Ninety-eight women diagnosed with CSP who underwent MRI evaluation between May 2016 and September 2023, and CSP was classified into three subtypes according to sac morphology, vascular characteristics, and scar myometrial thickness. Subgroups were further stratified by preoperative UAE status. Intraoperative blood loss during pregnancy termination, evaluated by regression analysis and intergroup comparison. Results: Thirty-five patients were classified as type I, 35 as type II, and 28 as type III. Type I CSPs typically showed simple cystic sacs with minimal vascularity, while type II exhibited moderate vascularity and mixed cystic-solid features. Type III was characterized by large mixed cystic-solid sacs with prominent vascular flow voids, vascular lakes, and arteriovenous fistulas. Median intraoperative blood loss was 20 mL for type I, 50 mL for type II, and 265 mL for type III ( Conclusion: Magnetic resonance imaging classification provides a reliable framework to stratify hemorrhage risk in CSP. Type III is associated with substantial intraoperative bleeding, and preoperative UAE is highly effective in mitigating this risk. Incorporating MRI classification into routine assessment may guide individualized management and improve surgical outcomes.