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Objective. To determine the usefulness of placental magnetic resonance imaging (MRI) in the diagnosis and surgical management of abnormal placentation. Design. Retrospective follow-up. Setting. Buenos Aires, Argentina. Population. 547 pregnant women. Methods. In all cases, a direct and reliable description of abnormal placentation features was obtained by the operating surgeon. Placental MRI was analyzed according to: (1) primary description, (2) invasion topography, (3) modification required to the surgical tactics or techniques and (4) by positive and negative predictive values. Main outcome measures. Ultrasound and MRI findings were compared with surgical results, which were considered a final diagnosis in relation to primary diagnostic indications. Results. Placental MRI was obtained because of diagnostic doubt in 78 cases, for deep invasion diagnosis in 148 cases and to define the invasion area in 346 cases. Placental MRI allowed accurate demarcation and assessment of the degree of placental invasion, parametrial involvement and cervico-trigonal vascular hyperplasia, permitting changes in the surgical tactical approach. Ultrasound and MRI differences were associated with placenta previa, uterine scar thinning and use of different criteria for placental invasion through definitions or terminology. Six cases of false-negative and 11 of false-positive findings were reported. Conclusion. Placental MRI provides excellent characterization of the degree and extension of placental invasion. Its usefulness in cases of adherent placentation is directly associated to the therapeutic measures, especially where dissection maneuvers are needed. Diagnostic differences between ultrasound and MRI related to the presence or not of placenta previa and uterine scar thinning. [ABSTRACT FROM AUTHOR]

Background: To establish the usefulness of placental magnetic resonance in patients with a diagnosis of placenta accreta through the correlation of diagnostic images and surgical findings., Methods: Three hundred patients with ultrasound signs of placenta accreta were studied. In 252 patients, magnetic resonance imaging (MRI) was performed in a closed 1.5 T-resonator, and in 48 patients, open 0.23 T-set was used. T1 and T2 slices in the three planes were performed, and placental invasion was classified in depth levels and topographic areas in relation to the posterior vesical wall. The final degree of invasion was established during surgery according to clinical and anatomical criteria. The information obtained with MRI was analyzed, thus establishing its relevance to the change in surgical technique., Results: In 286 cases, MRI provided topographic information of placental invasion, and in 90 patients, it modified invasion levels. Undiagnosed parametrium extent was determined in 11 cases, and 11 other cases were reclassified as placenta previa. Changes in conduct following MRI study included: recommendation to modify surgery date at week 35, recommendation for prophylactic ureteral catheterization, recommendation for the use of intraoperative blood salvage, possibility of approach through Pfannenstiel incision, probability of segmental myometrial approach, probability of aortic clamping, need to investigate subclinical disseminated intravascular coagulation, need of posterior pelvic dissection, and the possibility of uterine conservation., Conclusions: Magnetic resonance imaging turned out to be essential to define the topography and area of placental invasion. New findings modified surgical tactic and technique, allowing a reduction in historical morbidity and a significant increase in conservative surgeries.