Cesarean uterine scar pregnancy (CSP) is defined as a gestational sac lodging with the cesarean scar of the uterus. It is a relatively uncommon but high risk index ectopic pregnancy and is one of the distant complications of cesarean delivery (1). The exact etiology of the condition is not yet fully understood. Some studies (2, 3) have confirmed that in the period following cesarean section, the uterine scar becomes vascularized and rich in blood supply, which may explain the tendency of fertilized eggs to migrate to the vascularized area around the scar for implantation and implantation. It has also been found (4, 5) that more than 70% of CSP after cesarean section occur in those with a history of more than 2 cesarean sections, suggesting that enlarged, fibrotic, poorly formed local blood vessels and poor healing of the uterine scars after multiple cesarean sections are associated with the development of ectopic pregnancy there. In recent years, with the introduction of China's two- and three-child policy and the opening up of the public's ideology, the cesarean section rate of pregnant women has shown a clear upward trend, and the incidence of CSP has gradually increased. As a distant complication of cesarean delivery, CSP can lead to severe bleeding or even haemorrhagic shock in patients, with the possibility of uterine rupture and life-threatening effects of continued pregnancy (6–8).

Currently, there are many treatment options for CSP, including conservative treatment with methotrexate (MTX) alone and curettage, but the drawbacks of these options have gradually emerged with the widespread clinical application (9). The risk of hemorrhage and recurrence of CSP during re-pregnancy with medication alone is high, and is now often used as an adjunctive treatment during surgery; unclear indications for uterine removal can easily lead to intraoperative hemorrhage and even require uterine removal to preserve the patient's life and deprive the patient of fertility (10, 11). Uterine artery embolization (UAE) is a new minimally invasive interventional procedure that can rapidly and effectively control massive vaginal bleeding due to vascular injury. It has the advantage of being minimally invasive, with fewer side effects and fewer postoperative complications than uterine artery ligation, internal iliac artery ligation or hysterectomy, which were previously used to control massive vaginal bleeding (12, 13). In recent years this interventional technique has been widely used in the field of obstetrics and gynecology, especially in the treatment of postpartum hemorrhage (14), uterine fibroids (15) and cervical pregnancy (16), but there are still clinical concerns about whether UAE treatment of CSP will impair patients' reproductive function. In this trial, we treated CSP patients with UAE and analyzed its therapeutic effects as well as its impact on patients' serum Human chorionic gonadotropin (β-HCG) levels and fertility function.

As a long-term complication after cesarean section, CSP can lead to uterine rupture and placental implantation, increasing the incidence of hemorrhage and affecting sexual and reproductive function if not managed correctly (18, 19). The pathogenesis of CSP is not fully understood, but most scholars support the uterine incision defect theory (20, 21), which states that the uterine incision site is not fully healed after lower uterine cesarean section and is defective, thus making it easy for fertilized eggs to implant in the uterine incision scar where the endometrial defect exists. It has also been shown (22, 23) that the development of CSP may be closely related to the low position of the cesarean incision, multiple cesarean sections, defective suturing technique and postoperative incision healing, and wide scars. The currently accepted principles of CSP treatment (24) are early diagnosis, early termination of pregnancy and reduction of complications in order to preserve the patient's reproductive function reduce the trauma caused by surgery to the patient and achieve better outcomes.

In the past, hysterectomy was used as the only treatment option for CSP to avoid maternal mortality. In recent years, however, with the widespread use of ultrasound, CSP has been able to be diagnosed clearly at an early stage and conservative treatment has been widely used in clinical practice (25). Currently commonly used programs include systemic drug therapy, surgical therapy, and drug combined surgical therapy. MTX is a conservative drug commonly used in clinical practice, which can effectively preserve fertility by inhibiting trophoblast proliferation and causing necrosis of the villi cells, resulting in embryocidal effects (26, 27). UAE is an interventional procedure in which fresh gelatin sponge particles are introduced into the uterine artery to rapidly cause platelet coagulation and the formation of a thrombus, which can act as an embryocidal agent by blocking the blood supply to the embryo and can also greatly reduce the incidence of hemorrhage and preserve the patient's fertility (28, 29). In this study, the combination of local application of MTX, UAE and curettage for CSP patients showed that the intraoperative bleeding was lower in the research group than in the control group, and the time to get out of bed, postoperative vaginal bleeding, hospital stay, return to normal serum β-HCG and return to normal menstruation were all significantly shorter in the research group than in the control group; the recent efficacy of the research group was significantly higher than that of the control group (P < 0.05). It is possible that the thrombus has formed in the uterine artery and the ischaemic and hypoxic state has developed at the lesion by the time the uterine clearance is performed 48 to 72 h after UAE, which reduces the occurrence of intraoperative hemorrhage to a greater extent, decreases the amount of intraoperative bleeding and also shortens the duration of vaginal bleeding and hospital stay to a certain extent, which facilitates the patient's recovery (30). In this study, the levels of serum FSH, E2, LH and β-HCG and other reproductive hormones were also measured at different times, and the results showed that except for significant changes in serum β-HCG levels, the differences in the levels of other indicators between preoperative and 1 month postoperative were not significant. It is suggested that UAE treatment improves serum β-HCG levels in CSP patients without adversely affecting the secretory function of their ovaries. In addition, there was no difference in the normal pregnancy rate between the two groups during the follow-up period, but the recurrence rate of CSP in the research group was significantly lower than that in the control group, suggesting that UAE treatment is less damaging and more curative, and can preserve the patient's reproductive function to a greater extent, and has a good prognosis for pregnancy outcomes.

The results of this study also showed that the incidence of complications such as vomiting, fever and lower abdominal pain were significantly lower in the study group than in the control group. Analysis of the reasons for this: UAE interventions are able to form embolisms that block the circulation to the uterus, causing necrosis after the lesion is placed in an ischaemic and hypoxic environment (31). The local injection of MTX into the uterus prior to embolisation allows the local concentration of the drug to be at a high level, enabling the trophoblast to atrophy within a relatively short period of time. As the lesions become necrotic and the trophoblast cells are eliminated, the local concentration of MTX in the uterus is significantly reduced and less drug remains, thus reducing to a greater extent the risk of complications such as fever and vomiting associated with the application of MTX to the patient (32).

In conclusion, the use of UAE in CSP patients can reduce intraoperative bleeding and the duration of vaginal bleeding, promote the improvement of patients' clinical symptoms, have less impact on the disruption of patients' sex hormone balance, reduce patients' surgical risks to a greater extent, preserve patients' normal fertility, and have better results.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

The studies involving human participants were reviewed and approved by the Affiliated Huaian Hospital of Xuzhou Medical University. The patients/participants provided their written informed consent to participate in this study.

WZ and XZ are mainly responsible for data statistics and paper writing. CL and YL are mainly responsible for research design and result testing. WX is mainly responsible for the guidance of the entire research process. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.