Abstract: ［Abstract］ Objective〖HTSS〗〓To investigate the imaging characteristics of different types of placenta previa and to analyze the value of MRI in predicting massive hemorrhage and maternal and infant outcome after hysterectomy.
〖HTH〗〖WTHZ〗Methods〖HTSS〗〓Ninetyfive patients with placenta previa were divided into 24 cases of borderline placenta previa group, 18 cases of partial placenta previa group, and 53 cases of complete placenta previa group. The pregnancy outcomes of different types of placenta previa were observed. Ninetyfive patients were further divided into the bleeding group(32 cases) and the nonbleeding group(63 cases). Their age, number of births, history of caesarean section, history of miscarriage and types of placenta previa were observed, and the risk factors of postoperative bleeding were analyzed.
〖HTH〗〖WTHZ〗Results〖HTSS〗〓Comparison of maternal and infant outcomes of different types of placenta previa showed that the incidence of postpartum hemorrhage and hysterectomy rate of patients with complete placenta previa were higher than those with borderline placenta previa(P＜005). In the bleeding group, the proportion of births≥3 times, previous history of cesarean section, history of abortion, complete placenta previa, placental implantation, myometrium thinning, placenta penetration into the cervix, and uneven placental signals were all higher than those in the nonbleeding group(P＜005). Logistic regression analysis showed that previous history of cesarean section, complete placenta previa, placental implantation and myometrium thinning were risk factors for postpartum hemorrhage in patients with placenta previa after cesarean section.
〖HTH〗〖WTHZ〗Conclusion〖HTSS〗〓The imaging of placenta previa by MRI is clear and accurate. Among the patients with placenta previa, previous history of cesarean section, complete placenta previa, placental implantation, and myometrium thinning are the risk factors of bleeding after cesarean section with placenta previa.

Key words: placenta previa, cesarean section, postpartum hemorrhage； , magnetic resonance imaging