Study links caesarean scar endometrial defects to abnormal uterine bleeding

A Zhejiang University School of Medicine-led study says endometrial defects in caesarean scar defects play a bigger role in post-caesarean abnormal uterine bleeding than myometrial defects. The findings, published in BJOG, could change how clinicians identify and treat a common post-caesarean complication.

Why it matters: - Caesarean scar defect is a common complication after a caesarean section. - Abnormal uterine bleeding is the main symptom of caesarean scar syndrome. - The study suggests clinicians may need to look beyond myometrial thinning and diverticulum formation when evaluating bleeding after a caesarean section. - Better differentiation between endometrial and myometrial damage could support more targeted treatment.

What happened: - Researchers led by Dr. Jing Shu at Zhejiang University School of Medicine in Hangzhou, China, conducted a retrospective case-control study in two tertiary health centres. - The team compared hysteroscopic and pathological features of caesarean scar defects in patients with abnormal uterine bleeding and patients without it. - The study was published in BJOG: An International Journal of Obstetrics & Gynaecology on April 15, 2025, after online availability on February 7, 2025.

The details: - The research focused on caesarean scar endometrial defects, or CSEDs, as a driver of abnormal uterine bleeding. - Before matching, the abnormal uterine bleeding group had larger diverticulum sizes and more severe myometrial defects. - After propensity score matching for caesarean scar defect size and number of previous caesarean sections, the groups differed on endometrial defect features. - Those differences included in situ haemorrhage, bloody mucus, epithelial deficiency, and exposed and hyperplastic blood vessels. - In a subset of patients, pathology also showed significant differences in endometrial thickness at the caesarean scar, local vascularization and plasma cell count. - The paper concludes that, after controlling for myometrial defect severity, CSED features carried a significantly higher risk of abnormal uterine bleeding. - The original paper is titled "Caesarean Scar Endometrial Defects Contribute to Post-Caesarean Abnormal Uterine Bleeding and Chronic Endometritis: A Retrospective Case-Control Study". - The DOI is 10.1111/1471-0528.18089.

Between the lines: - The findings challenge the long-standing view that a diverticulum caused by partial myometrial separation is the main mechanism behind post-caesarean bleeding. - The researchers say endometrial epithelial defects may prevent the endometrium from fully covering the myometrium, which could help explain the bleeding. - The study also links CSED to possible changes in cervical and uterine microbiota, tissue exudation, abnormal metabolism, immune disruption, chronic endometritis and endothelial cell apoptosis. - That interpretation is mechanistic and broader than the measured comparisons, but it points to a more complex cause of symptoms than scar size alone.

What's next: - The findings may inform more precise diagnosis of post-caesarean abnormal uterine bleeding. - The study could also help shape new treatment strategies aimed at endometrial defects rather than only myometrial repair. - The researchers say this is the first study to connect CSED and abnormal uterine bleeding using hysteroscopic and pathological features. - Zhejiang University School of Medicine says the work was supported by the Medical Science and Technology Foundation of Zhejiang Province, grant 2019KY709. - More information is available in the journal site.