US Pregnant Uterus Transvaginal Transvaginal US scanning should be used in conjunction with transabdominal US scanning, particularly to evaluate the anterior lower uterine segment myometrium, placenta, and myometrial-placental interface because it can provide more detailed higher-resolution evaluation [15]. Variant 3: Follow-up of placenta accreta spectrum disorder. Women at high risk for PASD or with a known diagnosis of PASD should undergo a follow-up US to re-evaluate the evolving relationship between placental and umbilical vessel location, internal cervical os, placental edge thickness, internal architecture and morphology, and cervical length. These findings may highlight which patients are at highest risk for developing symptoms and complications and may need closer monitoring for potential earlier delivery. MRI Abdomen and Pelvis (Without and With IV Contrast) Regarding the use of MRI with IV contrast, there is no evidence to support gadolinium benefits and its ability to improve the delineation of placenta and myometrium because its use in pregnancy remains controversial, and currently there is no clear evidence to support its use for PASD [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% [17]. Gadolinium-based contrast agents are considered category C drugs, and use should be considered only if benefits outweigh the risks to the fetus. For example, contrast may be considered as an exception immediately prior to delivery or rare cases and circumstances in which termination is planned [14]. In summary, use of MRI in the diagnosis of this disorder is to be more supportive in the setting of a limited, difficult, or equivocal US study.
Placenta Accreta Spectrum Disorder. US Pregnant Uterus Transvaginal Transvaginal US scanning should be used in conjunction with transabdominal US scanning, particularly to evaluate the anterior lower uterine segment myometrium, placenta, and myometrial-placental interface because it can provide more detailed higher-resolution evaluation [15]. Variant 3: Follow-up of placenta accreta spectrum disorder. Women at high risk for PASD or with a known diagnosis of PASD should undergo a follow-up US to re-evaluate the evolving relationship between placental and umbilical vessel location, internal cervical os, placental edge thickness, internal architecture and morphology, and cervical length. These findings may highlight which patients are at highest risk for developing symptoms and complications and may need closer monitoring for potential earlier delivery. MRI Abdomen and Pelvis (Without and With IV Contrast) Regarding the use of MRI with IV contrast, there is no evidence to support gadolinium benefits and its ability to improve the delineation of placenta and myometrium because its use in pregnancy remains controversial, and currently there is no clear evidence to support its use for PASD [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% [17]. Gadolinium-based contrast agents are considered category C drugs, and use should be considered only if benefits outweigh the risks to the fetus. For example, contrast may be considered as an exception immediately prior to delivery or rare cases and circumstances in which termination is planned [14]. In summary, use of MRI in the diagnosis of this disorder is to be more supportive in the setting of a limited, difficult, or equivocal US study.