Purpose or Case Report: Although ultrasound remains main modality for prenatal diagnosis of fetal anomalies, fetal MRI has been increasingly recognized to provide additional information in various congenital pathologies. Usually, fetal MRI is performed at the time of diagnosis of the anomaly. Since fetal anomalies may evolve during pregnancy, a late 3rd trimester MRI may provide additional information, impacting postnatal management. This study aimed to evaluate the added value of repeat late 3rd trimester for diagnosis and patient management.
Methods & Materials: Retrospective study of patients that underwent 2 fetal MRIs during their pregnancy was conducted between 1/21 – 12/22. We reviewed the initial indication, MRI images, charts of mother/baby, site of delivery, impact of the second MRI on diagnosis and management, including in utero or postnatal interventions and final diagnosis.
Results: 320 patients underwent fetal MRI in the studied timeframe. 37 patients underwent a repeat MRI with continued care at our institution. Except one, all patients had the initial MRI during the 2nd trimester (average GA 22 weeks). All repeat MRI were performed in the 3rd trimester (average GA 32 wks). Indications were demarcated into the following categories; 9 gastrointestinal (GI), 11 neurology, 16 pulmonary pathology (PP), 1 vascular malformation.

Of the 9 GI, initial MRI at average 23, repeat at 31 wks GA. 5 improved diagnosis and characterization of pathology and 1 demonstrated normal findings after initial abnormal study. 3 had no change in diagnosis/management.

Of the 11 neurology, initial MRI average 21, repeat 32 wks. 4 had increase in size of ventriculomegaly. 1 improved diagnosis and characterization of pathology. 2 had resolution of initial ventriculomegaly. 3 underwent fetal surgery, with repeat MRI performed post intervention. 1 had no change in diagnosis.

Of the 16 PP, initial MRI average 22, repeat 33 wks. 3 patients had congenital diaphragmatic hernia and 10 patients had congenital lung malformation with repeat MRI change in lung volumes, 1 had a resolution of pulmonary effusion, 2 had initially diagnosed sequestration not seen on repeat MRI but surgically confirmed postnatally.

Vascular malformation patient (MRI at 21, 31, 36 wks). Repeat MRIs demonstrated increased size of the hemangioma.

84% of repeat MRI yielded additional information.
Conclusions: Repeat fetal MRI in the 3rd trimester can furnish valuable information that influences clinical management, particularly in cases of evolving or complex fetal anomalies.