Incidence of Uterine Isthmocele Following Cesarean Delivery: Retrospective Analysis of a Nationally Representative Database

INTRODUCTION: The development of uterine isthmocele—also known as cesarean scar defect or niche—is a potential long-term sequela after cesarean delivery, and may be associated with symptoms of abnormal uterine bleeding, pelvic pain, and infertility. Previous literature examining the prevalence of this condition consists of small cohort and case-control studies, which limits the accuracy of preoperative counseling and shared decision-making. Treatment can include hysteroscopic and/or laparoscopic excision and repair in symptomatic cases. OBJECTIVE: We aimed to describe the incidence of uterine isthmocele development after primary cesarean delivery. Secondary aims included investigating time from cesarean delivery to isthmocele diagnosis and diagnostic methods. METHODS: We performed a retrospective cohort study of individuals who underwent primary singleton cesarean delivery within the Vizient Clinical Database 2016–2023. Vizient is a healthcare performance improvement company that receives de-identified data from over 97% of academic medical centers and over 300 community hospitals across the United States. Isthmocele cases were identified using International Classification of Diseases (ICD)-10 codes and imaging findings. The primary outcome was incidence of uterine isthmocele, defined as number of cases of isthmocele divided by the person-time-at-risk after primary cesarean delivery. Secondary outcomes included time to isthmocele diagnosis and diagnostic methods associated with isthmocele identification. RESULTS: Overall, 2,191,417 individuals underwent primary cesarean delivery during the study period. The mean age of the cohort was 31.7 years (SD 6.3) at primary cesarean delivery. There were 308,748 (14.1%) isthmocele cases. These were identified by ICD-10 codes alone in 22.5% of cases, imaging findings alone in 52.0% of cases, and both ICD-10 codes and imaging findings in 25.5% of cases. Overall, 85.0% of isthmocele cases developed after the first cesarean delivery, 13.9% after the second, and 1.1% after the third or more. Mean time to diagnosis following the index cesarean delivery was 1.6 years (SD 1.1). The population incidence rate was 3,832.1 per 100,000 person-years after primary cesarean delivery. CONCLUSIONS: We found the population incidence of uterine isthmocele following cesarean delivery is 3,832.1 per 100,000 person-years in this cohort. These data should inform complete counseling regarding the risks of cesarean delivery, and we encourage clinicians to maintain a high index of suspicion for this condition in individuals who present with characteristic symptoms.