Objective:To explore the diagnostic value of fast imaging sequence of Magnetic Resonance Imaging (MRI) in placenta previa and prenatal placenta implantation .Methods:A total of 131 cases of pregnant women ,who had been diagnosed with placenta previa or suspected placenta implantation by ultrasonography and then underwent further MRI examination during June 2012 and June 2014 ,were enrolled ,and the diagnosis results were classified and summarized .MRI sequences included balanced fast field echo (B‐FFE) and single shot turbo spin echo (SS‐TSE) .Results:Quality of MRI images of 131 pregnant women was satisfactory .After childbirth ,43 cases were diagnosed as placenta implantation by surgery and pathology ,of which 3 cases were simple placenta implantation and 40 cases were placenta implantation combined with placenta previa .Among the 43 cases ,17 cases were adhesive placenta implantation ,and the other 26 cases were implantable and penetrative placenta implantation .Totally 22 cases with implantable and penetrative placenta implantation were diagnosed accurately (22/26 , 84 .62% ) by MRI ,while 5 cases were false positive and 4 cases were missed (false negative) ,thus the sensitivity was 84 .62% .Totally 14 cases with adhesive placenta implantation were diagnosed accurately by MRI(14/17 ,82 .35% ) ,while 3 cases were false positive ,thus the sensitivity was 82 .35% .The sensitivity ,specificity ,diagnostic accordance rate ,positive predictive value ,false positive rate ,and false negative rate of prenatal MRI examination for diagnosing placenta implantation were 83 .72% ,90 .91% ,88 .55% ,81 .82% ,9 .09% ,and 16 .28% ,respectively .Accordance rate of MRI for differentiating types of placenta previa was 100% .Conclusions:Fast imaging sequence of MRI has a high diagnostic value for abnormal location of placenta ,and it is an important verification and supplementary measure for positioning and determining abnormal placenta location .%目的：探讨磁共振（M RI）快速成像序列对前置胎盘、产前胎盘植入的诊断价值。方法：选择2012年6月—2014年6月因超声诊断前置胎盘或怀疑胎盘植入而进一步进行M RI检查的孕妇131例，对其诊断结果进行分类总结。M RI序列采用平衡式快速梯度回波（B‐FFE）和单次激发快速自旋回波（SS‐TSE）。结果：131例孕妇MRI图像质量满意。分娩后手术及病理诊断胎盘植入43例，其中3例为单纯胎盘植入，40例为前置胎盘合并胎盘植入；17例为粘连性胎盘植入，26例为植入性和穿透性胎盘植入。M RI准确诊断植入性和穿透性胎盘植入22例（22／26，84．62％），假阳性5例，漏诊（假阴性）4例，灵敏度为84．62％；M RI准确诊断粘连性胎盘植入14例（14／17，82．35％），假阳性3例，漏诊（假阴性）3例，灵敏度82．35％；M RI产前检查诊断胎盘植入的灵敏度、特异度、诊断符合率、阳性预测值、假阳性率、假阴性率分别为83．72％、90．91％、88．55％、81．82％、9．09％、16．28％。M RI对前置胎盘分型的符合率为100％。结论：M RI快速成像序列对胎盘位置异常具有较高的诊断价值，是对胎盘位置异常进行定位及定性的重要验证和补充手段。
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