Large Cesarean Scar Defects: Morphological Variants and Clinical Associations

Objective To characterize four post-cesarean sonomorphological subtypes of large anterior uterine wall defects after cesarean section and evaluate their association with clinical symptoms, infertility, endometriosis, and hysteroscopic findings suspicious for endometriosis within the scar defect. Design Prospective single-center cohort study. Subjects A total of 173 women with large cesarean scar defects undergoing surgical scar repair at a tertiary gynecologic center between April 2021 and January 2026. Exposure Post-cesarean sonomorphological subtype of the scar defect, classified as anteflexed uterus with niche, retroflexed uterus with niche, torqued uterus due to adhesions, or inclusion cysts at the uterotomy site. Main Outcome Measures Distribution of the four post-cesarean sonomorphological subtypes and their association with postmenstrual spotting, dysmenorrhea, abnormal vaginal discharge, dyspareunia, hypermenorrhea, infertility, intraoperatively diagnosed endometriosis, and hysteroscopic findings suspicious for endometriosis within the scar defect. Results Among 173 women, 38% had an anteflexed uterus with niche, 31% a retroflexed uterus with niche, 7% a torqued uterus, and 24% inclusion cysts. Postmenstrual spotting was the most common symptom, affecting 59% of patients, followed by dysmenorrhea in 46%, abnormal vaginal discharge in 39%, dyspareunia in 28%, and hypermenorrhea in 20%. Most symptoms occurred across all variants without statistically significant differences. Infertility was reported by 65% of patients overall and was most frequent in women with inclusion cysts (74%), although differences between variants were not statistically significant. Intraoperatively diagnosed endometriosis was present in 52% of patients and tended to be more common in retroflexed, torqued, and inclusion cyst variants than in anteflexed defects. Reddish deposits at the niche base, considered hysteroscopically suspicious for endometriosis within the scar defect, were observed in 89% of hysteroscopically assessed patients. Conclusion Large post-cesarean scar defects can be classified into four sonomorphological subtypes with overlapping clinical symptom profiles. The proposed classification enables differentiated anatomical assessment. The pathogenesis of the sonomorphological variants should be regarded as hypothesis-generating and require longitudinal validation.