Objective To explore the diagnostic value of MRI in placenta accrete with placenta previa by comparative magnetic resonance imaging (MRI) with ultrasonography (US). Methods US and MRI were performed in 20 pregnancy with placenta previa in 1 week. The sensitivity, specificity, positive predictive value and negative pre-dictive value of MRI and US were comparative studied by the standard of postoperative clinical data. The advantage of MRI in the placenta accreta was evaluated according to comparative analysis of the muscle-invasive of placenta on MRI and US. Results The sensitivities, specificities, positive predictive values and the negative predictive values were respectively, 93%, 83%, 93%and 83%in US, and 93%, 100%, 100%and 86%in MRI. MRI was more sensi-tive than US in the terms of muscle-invasive display with diagnostic accuracy rate of 75% and 50% respectively. Conclusion MRI could show the placenta accreta accurately, and should be routinely performed in the patient with placenta previa. MRI is more accurate than US in evaluation of the depth of placenta accreta.%目的：通过与超声的对比研究，评价磁共振在前置胎盘患者胎盘植入诊断中的应用价值。方法对20例临床怀疑胎盘植入的前置胎盘孕妇在1周内先后进行超声和磁共振检查。检查结果与分娩术后临床资料进行比较，评价超声和磁共振在诊断胎盘植入的敏感性和特异性。对超声和磁共振判断肌层侵犯情况进行比较分析，评价磁共振对超声在胎盘植入中的比较优势。结果超声和磁共振诊断胎盘异常的敏感性均为93％，特异性分别为83％和100％，阳性预测值分别为93％和100％，阴性预测值分别为83％和86％。在显示胎盘肌层浸润方面，磁共振较超声更敏感，诊断准确率分别为75％和50％。结论磁共振能对胎盘植入作出较准确的诊断，可以作为前置胎盘患者常规的筛查手段。磁共振对胎盘植入深度的显示较超声更准确。
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