Objective  To investigate the diagnostic effect of magnetic resonance imaging (MRI) on the pernicious placenta previa (PPP) with placenta implantation.

  Methods  The clinical data of 90 pregnant women confirmed as PPP comfirmed by MRI in our hospital were analyzed retrospectively. The results of operation and pathology were taken as the gold standard, the diagnostic effect of MRI on PPP, PPP with placenta implantation and their classifications were observed. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were calculated. The diagnostic consistency was compared between MRI and pathological results.

  Results  Among 90 cases with PPP, there were 24 cases with PPP alone, accounting for 26.67%, 66 cases with placenta implantation, accounting for 73.33%. The sensitivity, specificity and accuracy of MRI in diagnosing PPP complicating with placenta implantation were 92.42% (61/66), 87.50% (21/24) and 91.11% (82/90), respectively, and positive predictive value and negative predictive value were 95.31% (61/64) and 80.77% (21/26), respectively. Eight cases were misdiagnosed, including 5 cases complicating with placenta implantation were misdiagnosed as PPP alone and 3 cases with PPP alone were misdiagnosed as placenta implantation, with a total misdiagnose rate of 8.89%(8/90). The diagnosis of MRI for PPP combined with placental implantation had better consistence compared with the gold standard of surgical pathology (Kappa= 0.728, P < 0.05). Surgical pathology results showed that there were 66 cases with placental implantation, including 42.42%(28/66) of patients with adhesion type, 31.82%(21/66) with implantable type, and 25.76% (17/66) with penetration type, and the their detection rates of MRI were 82.14%(23/28), 90.48%(19/21) and 100.00%(17/17), respectively.

  Conclusion  MRI can better observe the relationship between placental tissue and myometrium of uterus, and has significant diagnostic value for PPP with placental implantation and typing, which can provide reliable imaging basis for clinical intervention.