Objective To explore the relationship between placental thickness,MRI signs and postpartum hemorrhage in placenta accreta(PA)patients.Methods 28 PA patients with postpartum hemorrhage and 3 9 PA patients without postpartum hemorrhage were analyzed retrospectively.We compared the clinical features and MRI signs between the two groups,and analyzed the correlation between placental thickness and PA related postpartum hemorrhage.Results The mean placental thickness was significantly higher in the hemorrhage patients (62.04±13.826)mm than that in the patients without hemorrhage (39.72±11.362)mm.Among the clinical features, there were no correlations between age,previous intrauterine operation history,previous cesarean section history and occurrence of the PA related postpartum hemorrhage.The following MRI signs were related to the occurrence of the PA related postpartum hemorrhage,including placenta previa,local bulging of the uterine,heterogeneous signal intensity in the placenta,intraplacental hypointensity bands,intraplacental abnormal vascularity,scar covered by placenta,abnormal signal intensity around the cervix,thinning of myometrium.Conclusion Measurement of placental thickness by MRI combined with placenta previa,local bulging of the uterine,heterogeneous signal intensity in the placenta,intraplacental hypointensity bands,intraplacental abnormal vascularity,scar covered by placenta,heterogeneous signal intensity around the cervix, thinning of myometrium are valuable in predicting PA related postpartum hemorrhage.