The additional value of fetal MRI to ultrasonography in prenatal diagnosis: an evaluation based on postnatal confirmation.

OBJECTIVES

To assess the additional diagnostic value of fetal magnetic resonance imaging (MRI) compared to prenatal ultrasonography (US) in fetal anomaly evaluation, using postnatal confirmation as the reference standard.

METHODS

In this retrospective cross-sectional study, we evaluated 104 fetal cases who underwent fetal MRI following suspicious or abnormal second- or third-trimester US findings between January 2022 and January 2025. US and MRI findings were compared, and diagnostic concordance was categorized. Postnatal confirmation was based on imaging, surgical, clinical, or pathological follow-up. Diagnostic accuracy rates were calculated using postnatal outcomes as the gold standard, and modality agreement was assessed using the kappa coefficient and McNemar test.

RESULTS

Postnatal confirmation data were available for 99 of the 104 cases, comprising 149 anomalies. MRI and US showed complete agreement in 79.8 % of cases. MRI provided additional diagnostic information over US in 10.6 % and showed discrepant findings in 9.6 %. Postnatal data confirmed that US correctly diagnosed 76.8 % of cases, while MRI reached 92.9 % diagnostic accuracy, a statistically significant difference (p=0.0015). The agreement between modalities was moderate (κ=0.54). MRI notably enhanced diagnostic accuracy, especially for central nervous system anomalies, and influenced postnatal clinical management.

CONCLUSIONS

Fetal MRI significantly improves prenatal diagnostic accuracy over US, particularly in complex or ambiguous cases, with the most significant added value seen in central nervous system pathologies. Its complementary role enhances prenatal counseling and postnatal planning. Larger multicenter studies are warranted to evaluate its contribution across different organ systems.