Improved Fetal Screening using 0.55T MRI - PROJECT SUMMARY This project will develop a new approach for secondary fetal screening in mothers with poor acoustic windows. Rationale: Major congenital anomalies occur in approximately 3% of all births and account for 20% of infant deaths. In patients with good acoustic windows, most cardiac and extracardiac malformations can be characterized by ultrasound. Fetal MRI is typically reserved for patients with central nervous system pathology, major pulmonary malformations, or extracardiac vascular malformations; its superior soft tissue contrast and large field of view refine the diagnosis and improve the family counseling, pregnancy management, and delivery planning, yielding fewer neonatal complications. However, women with oligohydramnios, obesity, adverse fetal lie, or late presentation to medical care often have poor acoustic windows that compromise the diagnostic utility of fetal ultrasound; these women are overrepresented in underrepresented and medically underserved minority populations. Approach: Fetal MRI represents an excellent alternative for imaging in these patients but its expense, inconvenience, lack of availability, and safety concerns currently limit its utilization in this context. Our hypothesis is that contemporary 0.55 Tesla wide bore MRI can provide rapid, secondary fetal screening for high-risk pregnancies, providing greater patient comfort, safety, and access, and these benefits will be especially strong in mothers with poor acoustic windows. Our specific aims are to: 1) assess the potential of 0.55T to serve as a secondary fetal screening modality in women with poor acoustic windows and diagnostically compromised ultrasound studies, 2) compare 0.55T fetal MRI image quality, diagnostic confidence, and ease of interpretation to clinically indicated 1.5T fetal MRI, and 3) to develop new 0.55T fetal MRI methods that leverage the advantages of this field strength. Broader Impact: This work signals a fundamental paradigm shift in the role of fetal MRI in prenatal diagnosis by improving the speed, comfort, safety, and diagnostic yield of fetal MRI. This project will determine if 0.55T MRI systems are suitable for siting in Maternal Fetal Medicine clinics.