Risk assessment of severe postpartum hemorrhage after invasive placenta accreta based on three-dimensional reconstruction of magnetic resonance imaging

BACKGROUND: The aim of this study was to investigate the significance and feasibility of risk assessments based on the three-dimensional (3D) reconstruction of magnetic resonance imaging (MRI) of invasive placenta accreta (IPA) to create individualized surgical protocols and perioperative management plans in late pregnancy. METHODS: MRI and clinical data of 36 pregnant women with IPA admitted to Southwest Hospital from January 2017 to June 2021 were retrospectively analyzed. The patients were divided into the following 4 groups: peripartum hysterectomy (PH), abdominal aortic balloon block (AABB), PH with AABB, and nonsurgical treatment. Each group was then divided into severe and nonsevere postpartum hemorrhage subgroups based on postpartum hemorrhage volumes of not more than 2,000 mL and more than 2,000 mL, respectively. The uteri, placentas, IPA, and urinary bladders in each group were segmented and 3-dimensionally reconstructed using Amira 5.2.2 (Visage Imaging, Richmond, Australia) software, and their surface areas and volumes were calculated. A multifactorial unconditional logistic regression analysis was performed to evaluate the 3D morphological parameters of postpartum hemorrhage and calculate the optimal threshold. RESULTS: The bleeding volume, IPA area, placental area:uterine area ratio, IPA area:placental area ratio, maximum depth of IPA, placental position score, IPA position score, and implantation volume were greater in the severe postpartum hemorrhage subgroup than in the nonsevere postpartum hemorrhage subgroup of all groups. In the multifactorial regression analysis, the areas under the receiver operating characteristic curve of the implantation area, implantation volume, maximum depth of implantation, and implantation area:placental area ratio exceeded 0.9 and correlated strongly with severe postpartum hemorrhage, while those of the uterine area, uterine volume, placental area, placental volume, and placental area:uterine area ratio were between 0.5 and 0.7 and correlated with severe postpartum hemorrhage. The threshold (cutoff values) determining severe postpartum hemorrhage were 20,286.25 mm(2) of the implantation area, 0.01271 of the implantation area:placental area ratio, 15.03 mm of the maximum depth of implantation, and 46,846 mm(3) of the implantation volume. CONCLUSIONS: The MRI 3D reconstruction of IPA and its adjacent structures can accurately display the location, anatomical morphology, and spatial relationship of IPA, which can be used to improve the accuracy of IPA diagnosis, predict postpartum hemorrhage, and provide optimized treatment decisions for obstetricians.