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Does MRI Help or Hurt When Making a Diagnosis of Placenta Accreta?

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Learning Objectives and CME/Disclosure Information

This activity is intended for healthcare providers delivering care to women and their families.

After completing this activity, the participant should be better able to:

1. Describe the current role of MRI compared to ultrasound in the diagnosis of Placenta Accreta Spectrum Disorder
2. Discuss the results of this study comparing the utility of MRI as an adjunct to ultrasound in the diagnosis of Placenta Accreta Spectrum Disorder

Estimated time to complete activity: 0.25 hours

Faculty:

Susan J. Gross, MD, FRCSC, FACOG, FACMG
President and CEO, The ObG Project

Disclosure of Conflicts of Interest

Postgraduate Institute for Medicine (PIM) requires instructors, planners, managers and other individuals who are in a position to control the content of this activity to disclose any real or apparent conflict of interest (COI) they may have as related to the content of this activity. All identified COI are thoroughly vetted and resolved according to PIM policy. PIM is committed to providing its learners with high quality CME activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of a commercial interest.

Faculty: Susan J. Gross, MD, receives consulting fees from Sema4, and has financial interest in The ObG Project, Inc.

Planners and Managers: The PIM planners and managers, Trace Hutchison, PharmD, Samantha Mattiucci, PharmD, CHCP, Judi Smelker-Mitchek, MBA, MSN, RN, and Jan Schultz, MSN, RN, CHCP have nothing to disclose.

Method of Participation and Request for Credit

Fees for participating and receiving CME credit for this activity are as posted on The ObG Project website. During the period from June 7 2018 through June 7 2021, participants must read the learning objectives and faculty disclosures and study the educational activity.

If you wish to receive acknowledgment for completing this activity, please complete the post-test and evaluation. Upon registering and successfully completing the post-test with a score of 100% and the activity evaluation, your certificate will be made available immediately.

For Pharmacists: Upon successfully completing the post-test with a score of 100% and the activity evaluation form, transcript information will be sent to the NABP CPE Monitor Service within 4 weeks.

Joint Accreditation Statement

In support of improving patient care, this activity has been planned and implemented by the Postgraduate Institute for Medicine and The ObG Project. Postgraduate Institute for Medicine is jointly accredited by the Accreditation Council for Continuing Medical Education (ACCME), the Accreditation Council for Pharmacy Education (ACPE), and the American Nurses Credentialing Center (ANCC), to provide continuing education for the healthcare team.

Physician Continuing Medical Education

Postgraduate Institute for Medicine designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Continuing Nursing Education

The maximum number of hours awarded for this Continuing Nursing Education activity is 0.2 contact hours.

Read Disclaimer & Fine Print

BACKGROUND AND PURPOSE: 

  • Incidence of Placenta Accreta Spectrum Disorder is rising  
    • Estimated at 1/500-1/300 pregnancies  
  • Ultrasound is the standard radiologic modality, while MRI remains controversial  
  • Einerson et al. (AJOG 2018) sought to determine if MRI contributes to the sonographic diagnosis of Placenta Accreta Spectrum Disorder

METHODS: 

  • Retrospective cohort study  
  • Participants 
    • Patients undergoing both ultrasound and MRI during 2nd and 3rd trimesters
    • Placenta Accreta Spectrum Disorder suspected (ultrasound or risk factors)  
  • Ultrasound risk factors 
    • Numerous echolucent placental lacunae | Loss of a normal retroplacental hypoechoic space | Loss of detectable myometrium | Bladder wall irregularity | Presence of abnormal subplacental vascularity 
  • Other clinical risk factors (if no suggestive US findings) included  
    • History of endometrial ablation or cavity-entering myomectomy | ≥3 cesarean deliveries in the setting of placenta previa | Suboptimal visualization of the placenta by US 
  • MRI decision left to MFM/surgical and radiology providers  
  • Diagnostic accuracy was verified by surgical and histopathologic diagnosis at the time of delivery 
  • Primary outcome  
    • Change in diagnosis from sonographic interpretation that could alter clinical management 
  • Secondary outcomes 
    • Correlation of radiologic diagnoses with surgical and histopathologic diagnosis

RESULTS: 

  • 78 patients were included   
  • Diagnosis that could alter clinical management occurred in 36% of cases 
  • MRI correctly  
    • Changed diagnosis in 19%  
    • Confirmed diagnosis in 44% 
  • MRI incorrectly  
    • Changed diagnosis in 17% 
    • Confirmed diagnosis in 21% 
  • MRI was not more likely to change a diagnosis in the 24 cases of posterior and lateral placental location compared to anterior location (33% vs 37%, P = .84) 
  • MRI resulted in overdiagnosis in 23% and in underdiagnosis in 14% of all cases 
  • In 14 severe Placenta Accreta Spectrum Disorder (percreta) cases, MRI altered only 2 diagnoses, both downgraded  
    • One was a correct downgrade to Placenta Accreta Spectrum Disorder (accreta and increta) and the other was an incorrect downgrade  
  • PPV for severe Placenta Accreta Spectrum Disorder 
    • MRI: PPV 61% (95% CI, 0.41–0.78) 
    • Ultrasound: PPV 73% (95% CI, 0.45–0.91) 
  • Proportion of accurate diagnoses with MRI did not improve over time despite increasing volume and increasing numbers of changed diagnoses

CONCLUSION: 

  • The addition of MRI to the assessment of Placenta Accreta Spectrum Disorder can often lead to an incorrect diagnosis  
  • The authors advise that MRI should not be used routinely as an adjunct to ultrasound in the diagnosis of Placenta Accreta Spectrum Disorder

Learn More – Primary Sources: 

Magnetic resonance imaging is often misleading when used as an adjunct to ultrasound in the management of placenta accreta spectrum disorders

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