| Research Objective:To analyze placental position and MRI signal characteristics in late pregnancy,and to explore the value of MRI diagnosis and the correlation between placenta previa and placenta accreta,and to investigate the diagnostic efficacy of various signs in assessing the depth of placental implantation.In order to provide reliable reference information for prenatal diagnosis of placenta previa with placenta implantation,and raise awareness of placenta previa with placenta implantation in late pregnancy,so as to reduce missed diagnosis rate and misdiagnosis rate of placenta previa with placenta implantation in prenatal diagnosis of MRI.To guide the clinicians to choose the appropriate delivery time and mode of delivery,so as to reduce the intraoperative bleeding and mortality.Methods:1.The Clinical information and MRI imaging data of 137 patients with placenta previa by ultrasound pregnancy examination from January 2016 to July 2017 was collected.Then comparing the result of MRI with surgical and pathological results.2.137 parturients with abnormal placental position were divided into the Pernicious placenta previa group(PPP group)and the non Pernicious placenta previa group(group n PPP).Analyzed the characteristics of various signs in the two groups.To explore the role of various signs in the diagnosis of placenta accreta by MRI.Then analyze the sensitivity,specificity,missed diagnosis rate and misdiagnosis rate of MRI diagnosis.and compare the difference of MRI diagnostic efficacy between group PPP and group n PPP with placental implantation.Results:1.Ultrasound examination of 137 cases of late pregnancy showed placenta low or placenta previa.16 cases of placenta low and 121 cases of placenta previa were diagnosed by MRI.The results of MRI diagnosis in 115 patients with placenta previa were consistent with the results of postpartum clinical diagnosis,and the coincidence rate was 83.9%.2.81 cases of complete placenta previa were diagnosed by MRI,and the coincidence rate was 100%.There were 19 cases of partial placenta previa,The diagnosis of the 6 cases were confirmed by Postoperative diagnosis,12 cases were diagnosed as complete placenta previa,and 1 cases were diagnosed as marginal placenta previa after operation.21 cases of marginal placenta previa were diagnosed by MRI,and 15 cases of them were diagnosed after operation.3.72 cases of placenta accreta were confirmed by operation and pathology,and63 cases were detected by prenatal MRI.The overall diagnostic efficiency was basically consistent with the operative result(gold standard)(Kappa=0.735,P<0.01).60 of the patients were diagnosed as complete placenta previa,accounting for 83.3%.4.Of the 70 cases of perilous placenta previa,Postoperative diagnosis of 45 cases of them with placental implantation,accounting for 64.3%.Higher than non perilous placenta previa(40.3%).The probability of placental implantation was different,?2=7.9,P<0.05.5.The sensitivity,specificity,diagnosis rate,missed diagnosis rate and misdiagnosis rate of MRI in the diagnosis of placenta accreta was 91.1%,72%,84.3%,8.9% and 28% in PPP group,and 88%,95%,89.6%,18.5% and 5% in n PPP group.Respectively,The misdiagnosis rate of MRI for the perilous placenta previa is much higher than that of the common placenta previa6.The highest detection rate of MRI in penetrating placenta was 100%(5/5).The lowest detection rate of MRI in adhesive placenta was 28.6%(2/7)in PPP group and 33.3% in n PPP group(3/9).Conclusion:MRI has high accuracy in the diagnosis of placenta preposition.Multi-directional imaging features can show the relationship between placenta lower margin and cervical intraoral area from multiple angles,and make accurate diagnosis.The placenta position in patients with partial placenta previa can be moved down to completely cover the cervix with the pregnant period progresses,and lead to the postoperative diagnosis is not consistent with the conclusion of prenatal diagnosis by MRI.Prenatal MRI also has better diagnostic efficiency of placenta implantation,the high soft tissue resolution and imaging sequence can provide multiple signs of assessment of myometrial and placental villi relationship,in order to improve the detection rate of uterine scar placenta implantation,and provide reliable reference for clinical treatment. |
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