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Fetal and Placenta MRLloyd Stambaugh, MD
Radia
Fetal MR Indications
• Fetal MR is most commonly used to assess the brain after an abnormal fetal sonogram• Absent CSP
• Ventriculomegaly
• Abnormal posterior fossa
• Most common Fetal MR abnormal findings• Absent corpus callosum
• Ventriculomegaly
• Dandy Walker variant
Less common indications
• Chest mass
• Abdomen/pelvic mass
• Spinal abnormality
MRI Safety and Pregnancy
• FDA requires MRI devices indicate the safety of MRI with respect to the fetus “has not been established.”
• 2007 ACR states all pregnant patients can receive MRI as long as the “risk-benefit ratio to the patient warrants that the study be performed.”
MRI Safety and Pregnancy
• Canadian study, all births > 20 gestation between 2003-2015
• 1.4M deliveries
• MRI rate 3.97 per 1000 pregnancies
• 1st trimester MRI stillbirth RR 1.68 (CI 0.97 to 2.9); adjust risk difference 4.7 per 1000 person-years
• No significant higher risk of congenital anomalies, neoplasm, vision or hearing loss.
• Conclusion – 1st trimester MRI exposure was not associated with increased risk of harm to the fetus or in early childhood.
JAMA. 2016 Sep 6;316(9):952-61
25 y.o. pregnant patient. Absent CSP and ventriculomegaly on ultrasound.
31 y.o. pregnant patient. Mild asymmetric ventriculomegaly.
Fetal Brain MR added value
• Meta-analysis of 27 articles, 1184 patients – compared US and MR of fetal brain
• US and MR agreed 65%
• MR showed additional/different pathology in 23%
• Compared with post-natal dx • MR agreed 80%
• US agreed 54%
• Fetal brain MR in addition to US improves diagnostic accuracy
J Matern Fetal Neonatal Med, 2016; 29(18): 2949-2961
Fetal MR additional value
• Systemic review of literature
• 13 articles, 710 fetuses
• MR confirmed US-positive findings in 65%
• Provided additional information in 22%
• MR additional findings changed management in 30%
• US/MR primarily agreed for ventriculomegaly, but more often disagreed for midline anomalies.
Ultrasound Obstet Gynecol 2014; 44: 388-393
Fetal MR additional value
• MERIDIAN Study -- Multicenter, prospective, cohort study with brain abnormality on US (16 fetal medicine centers, 570 patients)
• Diagnostic accuracy improved• 23% in 18-24 wk EGA group
• 29% in >24 week EGA group
• Overall accuracy• US 68%
• MR 93%
• MR provided additional information in 49% and changed prognosis in 20%
• MR influence on counseling• None 22%
• Minor 63%
• Major 15%
• MR contribution to management• None 12%
• Minor 53%
• Significant 26%
• Major 6%
• Decisive 3%35%
28 y.o. pregnant patient with abnormal ventricle on US
32 y.o. pregnant patient with abnormal posterior fossa on US, concerning for Dandy Walker
MR Placenta
Placenta Accreta Spectrum
• Risk factors• Previous cesarean section, particularly multiple
• Placent previa
• AMA
• Additional – multiparity/IVF/uterine surgery/fibroids/smoking/etc
• Placenta previa + 3 prior C-sections = 40% PAS
• No previa + 3 prior C-sections = <1% PAS
31 y.o. female at 28w2d with prior C-section, previa, and pain under C-section scar
34 y.o. pregnant female with prior C-section. Peripheral location of gestation sac in LUS
42 yo pregnant patient with abdominal pain & vomiting
Placenta percreta through right lower uterine segment. Large RLQ hematoma and hemoperitoneum.
36 y.o. pregnant female with prior C-section and probable placenta accreta/percreta by US
Placenta Accreta Spectrum – US vs MR
• US• Sensitivity 77% to 87%• Specificity 96% to 98%
• MR• Sensitivity 80% to 85%• Specificity 65% to 100%
• MR and US have similar sensitivity, but US is generally more specific
• MR is helpful• Posterior or lateral placenta• Extra-uterine organ involvement with percreta
Clinical Ob Gyn; vol 61, No4, 755-765
• Assessed 28 cases of suspected placenta accreta spectrum in third trimester; all cases received US & MR; surgical confirmation of diagnosis
• US• Sensitivity 0.96
• Specificity 0.6
• MR• Sensitivity 0.83
• Specificity 0.4
• Post-hoc MR structured scoring system improved sens 0.96/spec 0.6
J Matern Fetal Neonatal Med. 2020 Nov 12:1-4
Thank You
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