L26/P-844 Factors Associated with Isthmocele Formation After Cesarean Section: A Multicenter Case–Control Study

Abstract Study question Which demographic, obstetric, and gynecologic factors are independently associated with thepresence of isthmocele after cesarean section? Summary answer Adenomyosis, endometriosis, repeated cesarean sections, retroverted uterus, and emergencycesarean delivery were independently associated with isthmocele presence. What is known already Isthmocele (niche) was defined as a triangular orsemicircular hypoechoic defect at the cesarean scar site with a depth ≥2 mm. İt is a frequent long-term complication of cesarean section and has been associated withabnormal uterine bleeding, infertility, and pelvic pain. Surgical factors such as closure technique andcesarean timing have been implicated, while the contribution of underlying gynecologic conditionsremains incompletely understood. Study design, size, duration This was a multicenter retrospective case–control study including 760 women with a history of atleast one cesarean section. A total of 278 women with isthmocele were compared with 482 controlswithout isthmocele. Participants/materials, setting, methods Cases were women with an isthmocele, while controls had no detectable niche. Demographic, obstetric, and gynecologicvariables (age, body mass index, number of cesarean sections, uterine position, uterine closure technique, adenomyosis, and endometriosis)were collected. Adenomyosis wasdiagnosed when at least two MUSA direct criterions were present. Endometriosis was defined by the presence ofa ≥2 cm ovarian endometrioma on ultrasound or laparoscopicallyconfirmed disease. Multivariate logistic regression analysis was performed to identify factorsindependently associated with isthmocele formation. Main results and the role of chance Women with isthmocele had significantly higher body mass index, a greater number of previouscesarean sections, higher rates of adenomyosis and endometriosis, a higher prevalence ofretroverted uterus, and emergency cesarean delivery compared with controls (all p<0.05), whereasage, height, smoking status, time since last cesarean section, closure technique, and postpartuminfection rates did not differ significantly between groups. In multivariate logistic regression analysis,adenomyosis showed the strongest independent association with isthmocele (aOR 62.8), followed byendometriosis (aOR 9.4), increasing number of cesarean sections (aOR 4.7 per additional CS), and retroverted uterus (aOR 2.1), while elective cesareansection was independently protective (aOR 0.24). Ethical approval was obtained from the Ethics Committee of the Ufuk University Faculty of Medicine (approval no. 12024861-75). Limitations, reasons for caution The retrospective design limits causal inference, and detailed surgical variables such as suture material and surgeon experience could not be evaluated. Wider implications of the findings Underlying gynecologic conditions, particularly adenomyosis and endometriosis, appear to be key contributors to isthmocele formation and should be considered in risk stratification and preventive strategies following cesarean section. Trial registration number No