Prenatal MR imaging diagnosis of placental invasion

Purpose: The aim of the study was to evaluate the characteristic imaging features and performance of prenatal magnetic resonance (MR) imaging in the diagnosis of placental invasion. Methods: This retrospective study was approved by our institutional review board and written informed consent was waived. Twenty-eight patients (age range 26–39 years; mean age, 33.8 ± 3.1 years) with suspected placental invasion underwent prenatal MR imaging, including 7 patients with placental invasion and 21 without. Two radiologists assessed the presence of seven previously described MR imaging findings associated with placental invasion. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. The diagnostic performance was also determined by a receiver-operating-characteristic curve analysis. Results: Three MR imaging findings (uterine bulging, heterogeneous signal intensity in the placenta on T2-weighted images, and hypointense intraplacental bands on T2-weighted images) were significantly more common in patients with placental invasion than in those without (P = 0.020–0.023). The presence of at least two of these three imaging findings yielded a sensitivity, specificity, positive and negative predictive values, and accuracy of 100, 86, 67, 95, and 89%, respectively. Conclusions: The presence of at least two of the three characteristic prenatal MR imaging findings strongly supports a diagnosis of placental invasion.