Assessing the Role of Magnetic Resonance Imaging in the Management of Gravid Patients at Risk for Placenta Accreta

Rationale and Objectives: The role of magnetic resonance imaging (MRI) in the diagnosis of placenta accreta remains uncertain. The purpose of this study was to evaluate the incremental benefit of MRI after ultrasound (US) for a large cohort of gravid patients at risk for a placenta accreta. Materials and Methods: A retrospective review of outcomes in women with risk factors for a placenta accreta between November 1995 and February 2008 was performed. Inclusion criteria were high-risk women with abnormal placenta implantation on US or operative diagnosis of placenta accrete, with or without a prenatal MRI. Delivery mode, diagnosis, and transfusion requirements were compared. Results: Ranging in age from 19 to 43 years, with zero to five prior cesarean sections, 139 women met inclusion criteria. The MRI was performed in 28.7% (40/139). US, MRI, and operative diagnoses were highly correlated (P < .001). Women who underwent both US and MRI were more likely to deliver by cesarean hysterectomy (P < .001). When the cohort is stratified by outcome diagnosis (normal, previa, accreta), no difference in delivery mode is found; regardless of whether subjects were imaged by US alone or US and MRI. Transfusion requirements were highest in the US and MRI group (mean of 3.9 units vs. 0.9 units in the US only group, P < .001). Conclusion: This study fails to demonstrate that the incremental use of MRI for placenta accreta changes delivery mode in stratified analysis. Patients who underwent both US and MRI were most likely to have a cesarean hysterectomy delivery, and required more blood products, suggesting that undergoing tests may be indicative of an abnormal and at risk patient population.