To investigate the factors influencing of the massive hemorrhage during induced abortion of women with unwanted pregnancy after cesarean section, and to construct and evaluate the prediction model for the massive hemorrhage based on these influence factors. Methods: From February 2021 to February 2024, the clinical data of 300 women with unwanted pregnancy after cesarean section in the hospital were selected in this study. According to the ratio of 7:3, these patients were divided 210 cases for the setting model and 90 cases for the validation set. According to the presence or absence of the intraoperative massive hemorrhage, these women were divided into group A (women with intraoperative massive hemorrhage) and group B (women without intraoperative massive hemorrhage). The clinical data of these women were collected, and the influencing factors of the intraoperative massive hemorrhage of the women were analyzed by logistic regression. The prediction model was constructed according to the independent influencing factors of the intraoperative massive hemorrhage of the women. Receiver operating characteristic (ROC) curve was used to evaluate the efficacy of this prediction model for predicting of the intraoperative massive hemorrhage of the women, and the H-L test was used to test the calibration of this prediction model. Results: 300 women with
unplanned pregnancy after cesarean section were induced abortion successfully. 2 cases were withdrawn from the setting model due to their personal factors, there were 4 women without the complete data collected, and so 204 women were included for the setting model. There was 1 case without the complete data collected, and so 89 cases were included for the validation set. Finally, the data of 293 women were included in this study. The incidence of the intraoperative massive hemorrhage of 293 women was 24.6% (72/293), and among them, there were 24.0% (49/204) women for the modeling set and 25.8% (23/89) women for the verification set. There were no significant differences in the age, the times of cesarean section, the time since last cesarean section, the muscle thickness of inferior anterior uterine wall, the embryo termination situation, the mean diameter of pregnancy sac, and the distance from the gestational sac to the scar of the women between group A and group B (all P<0.05). Logistic regression analysis showed that the age ≥35 years old, the cesarean section ≥2 times, the short time from the last cesarean section, the small thickness of the lower segment of the anterior uterine wall, the large average diameter of the gestational sac and the short distance from the gestational sac to the scar of the women with the unwanted pregnancy after cesarean section were the risk factors of their massive hemorrhage during artificial abortion (all P<0.05). ROC curve showed that the area under the curve (AUC) of the nomogra of the model in the setting model or in the validation set for predicting the risk of intraoperative massive bleeding of the women was 0.955 or 0.896. The calibration curve of the model in the setting model or in the validation set showed that the predicted curve of the prediction model was close to the ideal curve, with the good consistency. Conclusion: The advanced age, the number of cesarean section, the mean diameter of the gestational sac, the short distance between pregnancy sac and scar, the short time since last cesarean section, and the thin muscle thickness of inferior anterior uterine wall of the women with unwanted pregnancy after cesarean section can affect the occurrence of their intraoperative massive hemorrhage during abortion, and the prediction model constructed based on which has good prediction efficiency and calibration, and this model is helpful for the early clinical prevention and treatment of the occurrence of the intraoperative massive hemorrhage of the women with unwanted pregnancy during abortion.