ABSTRACT Background: There is an increase in the prevalence of intermittent post menstrual spotting in women with previous one or more cesarean section with no sufficient study about the association between cesarean scar defect, cesarean scar defect ultrasound measurement and post menstrual bleeding, so this study is conducted to assess this association. So, we aimed to evaluate the relationship between the caesarean scar defect ultrasound measurement and post menstrual spotting in women with previous Cesarean section. Methods: The current prospective cohort study was conducted in obstetrics and gynecology outpatient & fetal medicine unit at Zagazig University Hospital on 48 Patients, who had a previous caesarean section and complained of unexplained abnormal uterine bleeding. All patients were evaluated clinically as well as by transvaginal ultrasound. Cesarean scar niche assessed by transvaginal sonography (TVS) with measurement of niche dimensions (length, depth, width and residual myometrium thickness) Results: We found a significant positive correlation between menstrual duration, width, depth, and spotting, a significant negative correlation between residual myometrium thickness (RMT) and spotting, and a weak negative correlation between adjacent myometrial thickness (AMT) and spotting. There was a significant positive correlation between dysmenorrhea, dyspareunia, PID, subfertility, and spotting. A significant weekpositive correlation between dysuria and spotting and a significant negative correlation between menstrual regularity and spotting. Conclusions:Caesarean scar defect ultrasound measurements could be used for prediction of post-menstrual spotting.