超声及MRI在胎盘植入诊断中的应用现状及评价

Application status and evaluation of ultrasound and MRI in diagnosis of placenta accreta

胎盘植入是胎盘绒毛因内膜缺陷而直接侵入子宫内膜,或胎盘直接种植到子宫肌层及浆膜层内。根据胎盘绒毛植入子宫肌层的深度,可将胎盘植入分为胎盘粘连、胎盘植入和胎盘穿通。超声和MRI是目前临床最常用于诊断胎盘植入的方法。超声已成为胎盘植入的首选检查方法;但当胎盘位于子宫后壁或需要判断胎盘植入深度时,超声检查结果不可靠。作为超声检查的辅助手段,MRI对于胎盘位于子宫后壁的患者具有较大优势,同时对于胎盘植入的分型(尤其对于胎盘穿通的患者)明显优于超声。对临床怀疑有胎盘植入高危因素的孕妇可先行超声检查;当超声诊断不明确、胎盘位于子宫后壁或不能判断其植入深度时,可进一步行MRI,以优化诊断率。

Placenta accreta occurs when the decidua is invaded by the chorionic villi or the placenta abnormally implants into the myometrium and serosa because of the defect of the decidua.Based on the degree of penetration of the chorionic villi,placental invasion can be graded into placenta accreta,increta or percreta.Ultrasound（US） and MRI have been widely used as diagnostic tools for placenta accreta.US has been regarded as the first-rate imaging modality for diagnosis of placental accreta,but the results of which might be unreliable for a posterior placenta or when estimating the degree of placenta accreta.MRI has been explored as an adjuvant modality for further improving the prenatal diagnosis of posterior placenta accreta.Besides,MRI is better than US for estimating the degree of placenta accreta（especially for placenta percreta）.US can be first used to evaluate women at high risk for placenta accreta.For cases with inconclusive ultrasound features or inconclusive degree,MRI will optimize diagnostic accuracy.