Caesarean scar endometrial defects play a prominent role and contribute more to post-caesarean abnormal uterine bleeding than myometrial defects, finds study
Inadequate incisional healing after caesarean section can lead to caesarean scar defects (CSDs) and syndrome, which is characterized predominantly by abnormal uterine bleeding (AUB). AUB has been thought to be caused by endometrial and myometrial defects, but their precise role remains unclear. Digging deeper, researchers compared the hysteroscopic features of CSD in patients with and without AUB. Their findings revealed that endometrial defects may be more strongly associated with AUB than myometrial defects.
Caesarean section, the most prevalent surgical procedure in obstetrics, is associated with long-term post-operative complications. Caesarean scar defect (CSD) is a common complication after caesarean section, caused by improper healing of surgical incisions. Sometimes, patients with CSD may experience caesarean scar syndrome, which is characterized by a predominant symptom called abnormal uterine bleeding (AUB). Partial separation or thinning of the uterine myometrium and the resultant formation of a pocket called diverticulum has long been thought to be the mechanism responsible for AUB. However, diverticulum formation does not always cause abnormal bleeding and the size of the CSD does not strictly correlate with the symptoms of caesarean scar syndrome. In addition to myometrial defects, endometrial defects in CSD are an under-recognised cause of AUB. Thus, differentiating between these two pathological mechanisms may help elucidate their contribution in the pathogenesis of AUB.
To elucidate this, a team of
researchers led by Dr. Jing Shu from Reproductive Medical Center, Zhejiang University School of Medicine, China, and Department of Gynecology and Department of Reproductive Endocrinology, Hangzhou Medical College, China, conducted a retrospective case–control study in two tertiary health centres with patients who underwent hysteroscopy. They compared the hysteroscopic and pathological features of CSD in those who experienced AUB with those who did not. To control for differences in myometrial defect severity, the researchers performed propensity score matching (PSM) based on CSD size and number of previous caesarean sections. This study was made available online on February 07, 2025, and was published in Volume 132 Issue S2 of
BJOG: An International Journal of Obstetrics & Gynaecology on April 15, 2025.
“Our aim was to explore the role of caesarean scar endometrial defects (CSEDs) in the pathogenesis of AUB. For this, we hypothesized that clinical manifestations of CSD might be linked to CSED features observed by hysteroscopy or pathology and could be used to identify CSED contribution to AUB,” says Dr. Yanpeng Wang, the first author.
Notably, the AUB group exhibited larger diverticulum sizes and more severe myometrial CSD defects than the non-AUB group before PSM. However, after PSM, significant differences in the features of endometrial defects between the two groups were observed. These included
in situ haemorrhage, bloody mucus, epithelial deficiency, and exposed and hyperplastic blood vessels.
Besides differences in hysteroscopic features of CSD between those who experienced AUB and those who did not, the researchers also examined differences in pathological features of a subset of patients from each group. Biopsies of the CSD surface and careful comparison of uterine endometrial features also revealed significant differences between the groups. Specifically, assessments revealed significant differences in endometrial thickness of CSD, local vascularization and plasma cell count at CSD between the two groups. Overall, it was observed that after PSM for caesarean scar myometrial defects, CSED features conferred a significantly higher risk of AUB.
These findings suggest that CSED is likely the real cause of AUB, mainly because the endometrium cannot completely cover the myometrium due to epithelial defects. In addition, CSED may disrupt the microbiota composition in the cervix and uterine cavity by increasing tissue exudation and bleeding, leading to abnormal metabolism and disordered immune responses. This in turn, may lead to apoptosis of endothelial cells and chronic endometritis.
Elaborating further on these findings, Dr. Shu says,
“Our study is the first to uncover the link between CSED and AUB using hysteroscopic and pathological features. It advances our understanding of AUB, paving the way for development of more targeted treatment strategies for this common post-caesarean complication.”