AbstractAimThis study aimed to ascertain whether the lower anterior myometrial thickness (MT) between the bladder and the gestational sac in early pregnancy can be used to predict clinical outcomes in women with cesarean scar pregnancy (CSP) after expectant management.MethodsWe retrospectively analyzed the clinical data and early pregnancy ultrasound images of 21 patients who received expectant management for CSP. Among them, 11 patients with serious complications during pregnancy, such as intraoperative blood loss ≥1000 mL or with severe forms of morbidly adherent placenta (MAP; placenta increta or placenta percreta), were assigned to group A. The remaining 10 patients without serious complications during pregnancy were assigned to group B. The difference in MT between groups A and B was analyzed using nonparametric Mann–Whitney U test.ResultsThere was a statistically significant difference in MT between the groups (U = 20.000, p = 0.013). The area under the receiver operating characteristics (ROC) curve was 0.818, and the optimal cut‐off value for MT was 3.3 mm.ConclusionLower anterior MT around the gestational sac was correlated with severe complications, such as massive intraoperative bleeding or severe forms of MAP in patients with CSP.