Grand Rounds

CMECNE

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

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 faculty, planners, and others in control of educational content to disclose all their financial relationships with ineligible companies. All identified conflicts of interest (COI) are thoroughly vetted and mitigated according to PIM policy. PIM is committed to providing its learners with high quality accredited continuing education activities and related materials that promote improvements or quality in healthcare and not a specific proprietary business interest of an ineligible company.

The PIM planners and others have nothing to disclose. The OBG Project planners and others have nothing to disclose.

Faculty: Susan J. Gross, MD, receives consulting fees from Cradle Genomics, 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 07/15/2022, 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 test and evaluation. Upon registering and successfully completing the test with a score of 100% and the activity evaluation, your certificate will be made available immediately.

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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