中文摘要：

目的：比较彩超和MRI在凶险型前置胎盘产前诊断中的价值。方法对20例疑诊凶险型前置胎盘患者分别进行彩超和MRI检查，与手术及病理结果作为金标准进行比较，对比两组诊断结果。结果经手术或病理证实20例患者中凶险型前置胎盘共8例。彩超组误诊1例，漏诊3例，符合率为87.54%；MRI组误诊1例，漏诊1例，符合率为88.78%，差异无显著性意义（P＞0.05）。结论彩超、MRI都是诊断凶险型前置胎盘的适宜方法，但MRI在对合并后壁胎盘植入的凶险型前置胎盘灵敏度高，漏诊率低。在彩超诊断不明确患者，可联合MRI检查，有望提高凶险型前置胎盘的产前诊断率，为临床治疗提供诊断信息。

英文摘要：

Objective To assess the value of color doppler ultrasound and MRI in the diagnosis of pernicious placenta previa. Methods 20 case of suspected pernicious placenta previa were diagnosed and analyzed by ultrasound retrospectively and MRI, respectively. Results Among the 20 cases confirmed by clinical and pathological, 8 cases were pernicious placenta previa. When analyzed by ultrasound retrospectively, one cases was false positive, and three cases were missed, the accuracy rate was 87.54%. When diagnosed by MRI, one case was false positive, and one case was missed, the accuracy rate was 88.78%. There was no significant difference between the two groups of patients （P〉0.05）. Conclusion Ultrasound and MRI are suitable methods to got definitely prenatal diagnosis of pernicious placenta previa. Because MRI might be more effective in the diagnosis of placenta accreta occuring on the posterior walls of the uterus, combined with Ultrasound and MRI are expected to improve the rate of prenatal diagnosis and help to make clinical decision.