Abstract: Objective  To investigate the risk factors of the formation of collateral artery in uterine artery embolization(UAE) for uterine scar pregnancy. 
Methods  In total, 127 patients with uterine scar pregnancy in our hospital were selected as the research subjects. All patients were observed during UAE operation. The incidence of collateral artery was evaluated and calculated. According to the formation of collateral artery, the patients were divided into collateral artery group and non-collateral artery group. A comparative analysis was performed on the basic data and clinical examination indicators of the two groups. The risk factors of collateral artery formation after UAE were analyzed by univariate analysis and multivariate Logistic regression analysis. 
Results  According to the statistical observation, 45 cases with collateral artery were found during UAE for uterine scar pregnancy, and the incidence was 35.43%. Univariate analysis showed that there was no significant difference in age, body mass index(BMI), smoking history, drinking history, gestational age, education level, time interval from the last cesarean section(C-section), history of hysteromyoma and other basic and clinical data between the two groups(P>0.05). There were significant differences in the incidence of placenta previa, pelvic inflammation, pregnancy complications, history of abortion, frequency of C-section between the two groups(P>0.05). Through the design of multiple Logistic regression analysis program and the corresponding variable assignment, the multivariate analysis showed that the history of placenta previa, the history of pelvic inflammation, the high incidence of complications during pregnancy, the history of abortion, and the number of C-section were the high-risk factors of collateral artery formation during UAE treatment for uterine scar pregnancy. 
Conclusion  There is a high incidence of collateral artery formation during UAE treatment for uterine scar pregnancy in our hospital, among which the history of placenta previa and pelvic inflammation, high incidence of complications during pregnancy, history of abortion surgery and more times of C-section are all independent risk factors of collateral artery formation, which should warrant attention of clinicians.

Key words: uterine artery embolization, pregnancy complications, cicatrix