Objective:To determine some associated factors for isthmocele formation 3 months after the treatment of cesarean scar pregnancy (CSP).Materials and Methods:This is a prospective consecutive case series of CSP managed by fertility preservation modalities at a single tertiary care center from May 2016 to March 2019 (n=95). Patients with a diagnosis of CSP were identified and followed prospectively to collect data on the patients’ demographics; detailed medical, surgical, and social history; symptoms; imaging and laboratory parameters at the time of CSP diagnosis and during treatment; treatment modalities, myometrial thickness; and outcomes in terms of isthmocele formation.Results:Mean myometrial thickness overlying scar pregnancy was significantly lower in the group with isthmocele formation, and the mean gestational age of scar pregnancy was also significantly lower in the group with isthmocele formation following treatment of scar pregnancy (p<0.05). Multivariate regression analysis was conducted to determine associations between certain variables and isthmocele development, which revealed that the gestational age of scar pregnancy and myometrial thickness were significantly associated with isthmocele formation.Conclusion:Myometrial thickness and gestational age of scar pregnancy were significantly associated with isthmocele formation 3 months after treatment.