Risk Assessment Of Severe Postpartum Hemorrhage After Invasive Placenta Accreta Based On Three-dimensional Reconstruction Of Magnetic Resonance Imaging

Background:Cesarean section history and placenta previa are independent high risk factors for invasive placenta accreta(IPA).With the change of China’s fertility policy,the fertility status has changed greatly,the fertility age increased,the proportion of the second pregnancy after cesarean section increased,and the IPA increased accordingly.The most common serious complication of IPA is postpartum bleeding,which causes hemorrhagic shock,emergency hysterectomy and even endangers the life of the gravida and the fetus.Therefore,it is particularly important to accurately classify placenta accrete spectrum disorders(PAS) before delivery to accurately assess the risk of postpartum bleeding.Currently,ultrasound scoring system and MRI scoring system evaluate the risk of postpartum bleeding of PAS,but there is no unified standard consensus.3 D reconstruction is based on 2 D MRI image delineation reconstruction,which is more three-dimensional than traditional ultrasound and MRI and 3 D measured placenta implantation parameters are more accurate.Objective:To investigate the significance and feasibility of risk assessments based on the three-dimensional(3D)reconstruction of magnetic resonance imaging(MRI)of IPA to create individualized surgical protocols and perioperative management plans in late pregnancy.Methods:MRI and clinical data of 36 pregnant women with IPA at the Southwest Hospital from January 2017 to June 2021 were retrospectively analyzed.The patients were divided into four groups:peripartum hysterectomy(PH),abdominal aortic balloon block(AABB),PH with AABB,and non-surgical treatment.Each group was then divided into severe and non-severe postpartum hemorrhage subgroups based on postpartum hemorrhage amount no more than2,000 and more than 2,000 m L,respectively.The uterus,placenta,IPA,and urinary bladder in each group were segmented and 3D-reconstructed using Amira 5.2.2 software,and their surface area and volume were calculated.The basic clinical data of the patients were statistically analyzed,and the nonparametric tests of MRI three-dimensional morphological parameters were performed.The receiver operating characteristic(ROC)curve was plotted to analyze the diagnostic values of the area,volume,and depth of IPA in the postpartum hemorrhage of fatal placenta previa with IPA.Calculate the area under the curve(AUC),sensitivity,specificity and Jordan index.AUC values of<0.5,0.5–0.7,0.7–0.9,and>0.9 had no,low,moderate,and high diagnostic values,respectively.Two-sided tests were performed,with an alpha of 0.05.The best critical value of MRI three-dimensional morphological parameters for predicting severe postpartum hemorrhage at the maximum of Yoden index.Results:1.The MRI 3D reconstruction can display the IPA and its adjacent structures from multiple angles,which is basically consistent with the intraoperative results.2.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 non-severe postpartum hemorrhage subgroup of all groups.Our statistical analysis results show that 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.3.The threshold(cut-off values)determining severe postpartum hemorrhage were20,286.25 mm~2of an implantation area,0.01271 of implantation area/placental area ratio,15.03 mm of maximum depth of implantation,and 46,846 mm~3of implantation volume.Conclusions:1.The MRI 3D reconstruction of IPA and its adjacent structures can accurately display the location,anatomical morphology and spatial relationship of the IPA.2.The depth,volume,and area of IPA and implanted area:placental area ratio were closely associated with the risk of severe postpartum hemorrhage.3.The MRI 3D reconstruction can calculate the threshold(cutoff points)determining severe postpartum hemorrhage such as the depth,volume,and area of IPA,and preliminarily obtain the risk parameters of severe postpartum hemorrhage,which may help clinicians to more accurately assess the risk of severe postpartum hemorrhage according to the imaging parameters obtained after 3D reconstruction based on MRI.