These results are mainly applicable for the anterior placenta (either low lying or previa) in patients with previous cesarean delivery [3]. As per the recently updated SMFM-ACOG-SGO consensus document, US evaluation is important, but the absence of US findings does not preclude a diagnosis of PASD [13]. In patients with known history of prior cesarean delivery and/or low placenta or placenta previa, special attention should be paid on first trimester or nuchal translucency scanning to determine if there is a low implantation or cesarean section scar pregnancy that has been associated with increased risk for PASD [6,10,22-25]. MRI Abdomen and Pelvis (Without and With IV Contrast) There is insufficient evidence to support the use of gadolinium based contrast agents in MRI for this indication because there is no literature clearly establishing improved delineation of placenta and myometrium and the use of gadolinium based contrast agents remains controversial in pregnancy [26,27]. One series using gadolinium contrast compared imaging findings to pathology and reported good accuracy of US, with sensitivity for placenta accreta of 77%, specificity of 96%, but improved accuracy with MRI with corresponding sensitivity of 88% and specificity of 100% [20]. Gadolinium-based contrast agents are considered category C drugs, and their use should be considered only if the benefits outweigh the risks to the fetus. For example, IV contrast may be considered as an exception immediately prior to delivery or, in rare cases, in circumstances in which termination is planned [14]. Placenta Accreta Spectrum Disorder MRI Abdomen and Pelvis (Without IV Contrast) MRI without IV contrast may play a complementary or selective role in situations in which US is equivocally nondiagnostic, severely abnormal in the setting of posterior placentation, or limited by obesity that limits US assessment [14,20,28-34].
Placenta Accreta Spectrum Disorder. These results are mainly applicable for the anterior placenta (either low lying or previa) in patients with previous cesarean delivery [3]. As per the recently updated SMFM-ACOG-SGO consensus document, US evaluation is important, but the absence of US findings does not preclude a diagnosis of PASD [13]. In patients with known history of prior cesarean delivery and/or low placenta or placenta previa, special attention should be paid on first trimester or nuchal translucency scanning to determine if there is a low implantation or cesarean section scar pregnancy that has been associated with increased risk for PASD [6,10,22-25]. MRI Abdomen and Pelvis (Without and With IV Contrast) There is insufficient evidence to support the use of gadolinium based contrast agents in MRI for this indication because there is no literature clearly establishing improved delineation of placenta and myometrium and the use of gadolinium based contrast agents remains controversial in pregnancy [26,27]. One series using gadolinium contrast compared imaging findings to pathology and reported good accuracy of US, with sensitivity for placenta accreta of 77%, specificity of 96%, but improved accuracy with MRI with corresponding sensitivity of 88% and specificity of 100% [20]. Gadolinium-based contrast agents are considered category C drugs, and their use should be considered only if the benefits outweigh the risks to the fetus. For example, IV contrast may be considered as an exception immediately prior to delivery or, in rare cases, in circumstances in which termination is planned [14]. Placenta Accreta Spectrum Disorder MRI Abdomen and Pelvis (Without IV Contrast) MRI without IV contrast may play a complementary or selective role in situations in which US is equivocally nondiagnostic, severely abnormal in the setting of posterior placentation, or limited by obesity that limits US assessment [14,20,28-34].