Purpose: To determine the utility of magnetic resonance imaging (MRI) in diagnosing invasive placenta (IP).
Materials and methods: MRI findings in 32 women with suspected IP were evaluated independently by four readers. Interobserver agreement was calculated with kappa (κ) statistics. Associations between MRI findings and IP were assessed by univariate and multivariate analyses. Sensitivity, specificity and accuracy of MRI for the diagnosis of IP were estimated.
Results: Sixteen women (16/32; 50%) had confirmed IP. Interobserver correlation for the diagnosis of IP was fair (κ = 0.40). Univariate analysis revealed that thinning or focal defect of the uteroplacental interface (P < 0.0001) was the most discriminating MRI variable in the differentiation between normal and IP. Overall sensitivity and specificity of MRI for the diagnosis of IP were 84% [95% CI: 75-94%] and 80% [95% CI: 66-93%], respectively. Thinning or focal defect of the uteroplacental interface was the most accurate finding (88%) in the diagnosis of IP. Multivariate analysis revealed that thinning or focal defect of the uteroplacental interface was the single independent predictor of IP (P = 0.0006; OR = 64.99).
Conclusion: MR imaging has 84% sensitivity [95% CI: 75-94%] and 80% specificity [95% CI: 66-93%] for the diagnosis of IP. Thinning or focal defect of the uteroplacental interface is the most discriminating independent MR variable in differentiating between normal placenta and IP.
Key points: MR imaging has acceptable degrees of accuracy to diagnose invasive placenta. Focal uteroplacental interface defect is the best finding to diagnose invasive placenta. Focal uteroplacental interface defect is the single independent predictor of invasive placenta.