Impact of cesarean scar defects on the success of assisted human reproduction: The NICHE- ART prospective cohort study protocol

Abstract Background: The prevalence of caesarean sections worldwide continues to rise, increasing the risk of obstetric complications. Isthmocele, defined as a dehiscence of the hysterotomy following a caesarean section, can lead to intermenstrual bleeding or pelvic pain. Studies have shown that surgical treatment of isthmoceles reduces the incidence of metrorrhagia. In these studies, the authors noted that patients with abnormal bleeding outside the cycle were also more frequently affected by secondary infertility. However, isthmocele surgery can result in intrauterine adhesions and synechiae, which are also recognized as potentially deleterious to fertility. The impact of the presence of an isthmocele on the results of ART must therefore be demonstrated before any attempt at treatment, and this will require larger-scale prospective studies, using a consensus definition of the isthmocele based on sonohysterography (currently considered the "gold standard" examination). Methods: We designed a multicentric prospective study that will be conducted in 10 French Reproductive Medicine centers. We will include women consulting for infertility with a history of scarred uterus. During sonohysterography and transvaginal ultrasound, a specific measurement is taken to define the presence or absence of an isthmocele, and to classify patients into one of two groups: "isthmocele +" or "isthmocele -". The main objective of the study is to investigate the association between the presence of an isthmocele and the clinical pregnancy rate obtained after in vitro fertilization in patients with a scarred uterus (single or multi-scarred). The primary outcome is clinical pregnancy rate, as defined by the visualization of gestational sac on the transvaginal ultrasound. We will need to include 250 women with a scarred uterus undergoing ART. The duration of the inclusion period is estimated to be 42 months. Discussion: If our study shows a reduction in the clinical pregnancy rate in the presence of an isthmocele, this could lead to a change in clinical practices for patients undergoing ART. Indeed, surgical management of the isthmocele could be discussed prior to ART by informing the patient of the benefit-risk balance of the operation. Trial registration: ClinicalTrials.gov, ID:. NCT04869007. Registered on August 16th, 2020.