565: Predictors of carrier screening for Fragile X syndrome

individual diagnoses, the following test characteristics were considered: cases where MRI confirmed a correct diagnosis obtained by US, cases where MRI improved diagnostic accuracy by diagnosing anomalies that US did not, cases where MRI failed to confirm a diagnosis that was accurately obtained by US, and cases where MRI offered no benefit because neither MRI nor US accurately diagnosed the anomaly. RESULTS: 799 MRIs were performed, of which 406 subjects possessed documented neonatal or pathologic outcomes. MRI agreed with ultrasound in 68% of cases. Overall, MRI confirmed the neonatal diagnosis in 56.4% of cases, improved the diagnosis in 12.8% of cases, detracted from the diagnosis in 5.9% of cases, and had no benefit in 24.9% of cases. Among individual anomalies, there were no cases of diaphragmatic hernia, omphalocele, vein of Galen malformation, or Dandy Walker complex where MRI correctly changed the ultrasound diagnosis. Findings varied for all other diagnoses (Table). CONCLUSION: Fetal MRI generally agrees with US performed at a tertiary care center, which may limit its adjunct diagnostic benefit. For most diagnoses, MRI gains must be weighed against potential drawbacks prior to clinical use. Notably, this study does consider potential cost, prognostic, or surgical-planning benefits of fetal MRI.