Long-Term Complications of Caesarean Section, the Niche in the Scar: A Prospective Cohort Study on Niche Prevalence and its Relation to Abnormal Uterine Bleeding

Background: There have been several reports of an association between abnormal bleeding and a niche in particular, postmenstrual spotting seems to be a predominant symptom in women with a niche.   
Aim of the Work: To study the prevalence of niches in the caesarean scar in a random population, and the relationship with postmenstrual spotting.  
Patients and Methods: This prospective cohort study was performed on a total of 80 patients who underwent at least 1 lower segment caesarean section of single full-term pregnancy and conducted at Ain Shams University Hospital from April 2021 to December 2022. During this study, 100 patients were assessed for eligibility and 80 patients were included in the study. Of all eligible patients, 14 patients were excluded from the study based on the inclusion criteria and 6 patients refused to participate in of the study. 
Results: Regarding TVUS and 3D findings of scar niche at weeks 6-12 and at month 6, our results revealed that there were no statistically significant differences according to scar niche regarding menstruation, premenstrual spotting, while Menstrual irregularity, BAC score, durations of menstruation, intermenstrual bleeding and postmenstrual spotting statistically were significantly higher among cases with scar niche. Our study results revealed that menstrual abnormalities and postmenstrual bleeding were statistically significantly found in cases with higher niche depth. Our study results revealed that there were no statistically significant differences according to menstrual abnormalities at week 6-12 regarding residual myometrium thickness with significantly lower ratio of residual myometrium thickness in cases with menstrual abnormalities except in intermenstrual spotting.
Conclusion: caesarean section scar was visible in all women at 6–12 weeks after caesarean section. The prevalence of niches detected by 3D is high after caesarean section (56.6%), and more niches are detected than using TVUS (41.3%), with a larger observed niche size and reduced residual myometrial thickness. The presence of a niche is significantly related to postmenstrual spotting.