Human chorionic gonadotropin levels of cesarean scar pregnancy compared with those of other ectopic pregnancies: a retrospective cohort study

A cesarean scar pregnancy (CSP) is an abnormal implantation of an embryo within a previous cesarean section scar and considered a relatively rare form of ectopic pregnancy. We aimed to clarify the factors associated with CSP and evaluate whether differences in serum human chorionic gonadotropin (hCG) levels according to implantation site could contribute to early detection of CSP. We investigated 27,528 freeze-thawed embryo transfer cycles performed at our hospital between January 2016 and March 2025. Forty-four patients were diagnosed with ectopic pregnancy: 26 had tubal pregnancies, 10 had cervical pregnancies, 5 had CSP, 2 had peritoneal pregnancy, and 1 had an ovarian pregnancy. History of myomectomy and ≥ 2 cesarean sections showed significant differences in the logistic regression analysis (history of myomectomy: P = 0.003, history of > 2 cesarean sections: P = 0.006). The hCG levels (median [interquartile range {IQR}]) for ectopic pregnancy were 58.15 mIU/mL (33.0–100.3) for cervix, 179.0 mIU/mL (150.8–294.1) for CSP, 24.3 mIU/mL (8.8–49.7) for fallopian tube, and 9.1 mIU/mL for others (ovary and peritoneal pregnancy). There was a significant difference between CSP and all non-CSP ectopic pregnancies combined ( P = 0.001). The hCG level for clinical intrauterine pregnancy was 235.6 mIU/mL (136.6–382.4). There was a significant difference in hCG levels between clinical pregnancy and ectopic pregnancy ( P < 0.001), but this significant difference disappeared when clinical pregnancy was compared with CSP ( P = 0.607). Serum hCG levels in early pregnancy were higher in CSP than in other ectopic pregnancies. Even in the presence of high serum hCG levels during early pregnancy, CSP should be considered if there is a history of cesarean section, especially > 2 cesarean deliveries. The study included only five CSP cases, one of which was a duplicate case from a different treatment cycle. Consequently, the findings should be considered exploratory. Given the limited sample size, additional cases should be included and the statistical analysis repeated to ensure the robustness of the results.