Use of magnetic resonance imaging and ultrasound in the antenatal diagnosis of placenta accreta.

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To determine whether magnetic resonance imaging (MRI) and ultrasound (US) are effective methods for diagnosing placenta accreta, increta, or percreta antenatally. We retrospectively reviewed radiologic reports of patients who had the diagnosis of placenta accreta, percreta, or increta by pathologic analysis. The gestational age at first ultrasound diagnosis of accreta and first MRI diagnosis of accreta was recorded. Ultrasound and MRI reports were examined for findings of a distorted retroplacental myometrial zone, disrupted uterine-bladder interface, focal exophytic masses, and presence of vascular placental lacunae. Surgical history, cesarean hysterectomy, and blood loss were also recorded. Thirteen patients were identified, and 14 had true pathologic confirmation of accreta, increta, or percreta. Nine of thirteen had MRI, and of those, seven received gadolinium. Placenta accreta was diagnosed by MRI in five of nine patients, but only four were confirmed pathologically to have accreta. Four women who had a normal MRI had accreta confirmed by pathology (sensitivity 38%). Of the 13 patients who had US, four were considered to have an accreta, and these four had pathologic confirmation. Nine were negative for accreta by US; however, eight of those women had pathologic confirmation of accreta, and one was normal (sensitivity 33%). Both MRI and US had poor predictive value in the diagnosis of placenta accreta, and further refinement in the techniques of both MRI and US is needed for these tests to be used to reliably diagnose these pathologic conditions.