Currently, research interest in CSP has shifted from image-based diagnosis to optimal management. Regarding CSP management, the primary focus is on selecting the best treatment modalities to reduce complication risks and preserve fertility. Surgical and non-surgical treatments are the main modalities for treating CSP. For different types and severities of CSP, choosing the appropriate surgical approach can significantly impact treatment outcomes. For example, Xu et al. 16 adopted different measures for different types of CSP during lesion excision surgery to achieve optimal treatment outcomes. Additionally, reducing treatment complications through improved surgical techniques is also a focal point of CSP management. For instance, Ellen Hofgaard et al.17 achieved better clinical outcomes in treating CSP by employing robot-assisted laparoscopy. Preoperative interventions can also reduce surgical risks18. In our meta-analysis on CSP treatment 19, it was found that preoperative UAE or HIFU can increase the success rate of surgery and significantly reduce postoperative complications after D&C. Long-term reproductive outcomes of CSP are also a focal point 20,21, especially for patients with fertility requirements. In summary, before selecting the optimal treatment modality, a detailed assessment of CSP is necessary to achieve the best treatment outcomes and avoid serious complications.
In previous reports, most studies11,22–24 were single-center, utilizing univariate and multivariate logistic regression analyses to identify clinical and/or imaging indicators for determining risk factors for massive bleeding or RPOC during CSP termination of pregnancy. In this study, we developed and validated, for the first time, a column chart-based lasso regression method to select ultrasound indicators for preoperatively predicting the risk of bleeding or RPOC during CSP curettage management. This nomogram incorporates four ultrasound measurements of CSP, including scar thickness, gestational sac diameter, and blood flow, and CSP type as relevant risk factors for CSP, to achieve personalized prediction of occurrence adverse events in CSP patients. The nomogram established via ultrasound indicators assists clinicians in screening cases with high risks of postoperative complications, such as intraoperative bleeding ≥ 200 ml or RPOC, thereby guiding clinicians to formulate appropriate treatment plans for patients, such as selecting experienced emergency specialists for treatment, performing operations to reduce blood supply to the gestational sac preoperatively, and preparing for blood transfusion intraoperatively, to maximize minimizing patient suffering and ensuring patient safety to the greatest extent possible.
Studies have reported5 that patients with CSP experience significantly higher levels of bleeding during D&C compared to those during miscarriage and abortion. This may be attributed to the attachment of the CSP gestational sac to the scar tissue of the uterine muscle layer, where the lack of decidua tissue makes it easier for trophoblastic cells to invade beyond the junction of the endometrium and uterine muscle layer, reaching the deep uterine blood supply from the radial and arcuate arteries 25, leading to a rapid increase in blood flow around the gestational sac. Therefore, forcibly separating the gestational sac during D&C may result in uncontrolled bleeding due to the weak muscle layer's inability to contract. Additionally, as the gestational age increases, the pregnancy mass enlarges, potentially elongating and thinning the lower segment of the uterus, coupled with an adequate blood supply, leading to increased bleeding during the surgical procedure. Thus, it is believed that the thinner the uterine muscle layer in the anterior wall scar, the more pronounced the increase in blood flow around the gestational sac site of the previous cesarean section incision, and the greater the likelihood of significant intraoperative bleeding.
The incidence of RPOC in patients with CSP is higher than that in those after miscarriage5,26,27. The possible reasons for the persistent residual mass of ectopic pregnancy are as follows: 1) The CSP mass enters the uterine muscle layer or scar depth through micro-fissures, such as in type III CSP, and may sometimes invade the broad ligament, making surgical excision difficult 28; 2) In case of significant intraoperative bleeding before complete emptying of the pregnancy product, surgery must be stopped to ensure hemostasis; 3) Local bleeding occurs before the complete removal of the gestational sac; and 4) Scar tissue at the uterine incision site may hinder its complete removal. Additionally, CSP patients typically undergo multiple routine follow-up examinations after surgery, which helps to improve the diagnosis rate of RPOC. Time is also crucial for terminating CSP, as with time, the gestational sac and its blood vessels grow, increasing the difficulty of D&C and the likelihood of residual RPOC 4. When trophoblastic tissue is situated at the scar site and the uterine muscle layer is thinner, there is an elevated risk of uterine perforation during D&C surgery. Additionally, a richer blood flow around the gestational sac increases the likelihood of bleeding during the procedure. These factors compound the surgical difficulty and may escalate the likelihood of RPOC. Consequently, for patients at a higher risk, personalized treatment plans such as hysteroscopy surgery or laparoscopic monitoring are preferable options.
There are several limitations to this study. Firstly, both the internal and external cohorts of this study come from different hospitals in the same province, limiting the external generalizability of the results. Secondly, this study is a retrospective cohort study, which cannot control for the consistency and completeness of data collection. Thirdly, the nomogram exclusively incorporated ultrasound-related indicators, which restricts the model's practicality in patients with unclear ultrasound images.