MRI Abdomen and Pelvis (Without IV Contrast) There is no relevant literature to support the use of MRI without IV contrast in the initial imaging evaluation for low-risk pregnancy unless concerning findings are present on routine US [13]. US Duplex Doppler Pregnant Uterus Doppler evaluation should be considered if any abnormalities of placental tissue or in the placental myometrial interface are detected on grayscale imaging regardless of placental location [4,14]. US Pregnant Uterus Transabdominal Routine transabdominal US evaluation of placental location, appearance, and its relationship to internal os is done as documented in the ACR-ACOG-AIUM-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetrical Ultrasound [15]. US Pregnant Uterus Transvaginal Transvaginal (or transperineal) US views may be helpful in visualizing the internal cervical os and its relationship to the placenta if not clear on transabdominal US [15]. Variant 2: High risk for placenta accreta spectrum disorder. Initial Imaging. The main risk factors for PASD include prior uterine surgery, including myomectomy, dilatation, and curettage, most notably cesarean delivery with concomitant anterior placenta previa, followed by advanced maternal age and in vitro fertilization. As many as 40% of women with placenta previa and three prior cesarean deliveries will develop PASD [8-10]. Women with high risk based on clinical history and/or US findings should be considered for referral for specialist imaging to confirm or exclude this diagnosis. Numerous studies have evaluated the use of US for the diagnosis of placenta accreta. US sensitivities have been reported to range from 77% to 97% with specificities of 96% to 98%, positive predictive value of 65% to 93%, and negative predictive value of 98% for PASD [16-21]. A meta-analysis of over 3,500 patients showed US to have high accuracy for diagnosing abnormal placentation, which improved with the addition of color Doppler [3].
Placenta Accreta Spectrum Disorder. MRI Abdomen and Pelvis (Without IV Contrast) There is no relevant literature to support the use of MRI without IV contrast in the initial imaging evaluation for low-risk pregnancy unless concerning findings are present on routine US [13]. US Duplex Doppler Pregnant Uterus Doppler evaluation should be considered if any abnormalities of placental tissue or in the placental myometrial interface are detected on grayscale imaging regardless of placental location [4,14]. US Pregnant Uterus Transabdominal Routine transabdominal US evaluation of placental location, appearance, and its relationship to internal os is done as documented in the ACR-ACOG-AIUM-SMFM-SRU Practice Parameter for the Performance of Standard Diagnostic Obstetrical Ultrasound [15]. US Pregnant Uterus Transvaginal Transvaginal (or transperineal) US views may be helpful in visualizing the internal cervical os and its relationship to the placenta if not clear on transabdominal US [15]. Variant 2: High risk for placenta accreta spectrum disorder. Initial Imaging. The main risk factors for PASD include prior uterine surgery, including myomectomy, dilatation, and curettage, most notably cesarean delivery with concomitant anterior placenta previa, followed by advanced maternal age and in vitro fertilization. As many as 40% of women with placenta previa and three prior cesarean deliveries will develop PASD [8-10]. Women with high risk based on clinical history and/or US findings should be considered for referral for specialist imaging to confirm or exclude this diagnosis. Numerous studies have evaluated the use of US for the diagnosis of placenta accreta. US sensitivities have been reported to range from 77% to 97% with specificities of 96% to 98%, positive predictive value of 65% to 93%, and negative predictive value of 98% for PASD [16-21]. A meta-analysis of over 3,500 patients showed US to have high accuracy for diagnosing abnormal placentation, which improved with the addition of color Doppler [3].