The role of MRI in the prenatal diagnosis and classification of fetal microtia

OBJECTIVE: To investigate the role of MRI in the diagnosis and classification of fetal microtia. METHODS: Ninety-five fetuses with suspected microtia based on ultrasound and MRI performed within 1 week were enrolled in this study. The diagnosis based on MRI was compared with postnatal diagnosis. Among the microtia cases suspected on the basis of MRI, mild and severe cases were further classified. In addition, external auditory canal (EAC) atresia was evaluated by MRI in 29 fetuses with a gestational age > 28 weeks, and the accuracy of MRI in the diagnosis and classification of microtia was determined. RESULTS: Of 95 fetuses, 83 were considered to have microtia on the basis of MRI, 81 were confirmed to have microtia, and 14 were found to be normal according to postnatal diagnosis. Among 190 external ears in 95 fetuses, 40 ears were suspected to have mild microtia, and 52 ears were suspected to have severe microtia on the basis of MRI. According to the postnatal diagnosis, mild and severe microtia were confirmed in 43 and 49 ears, respectively. Among the 29 fetuses with a gestational age > 28 weeks, 23 ears were suspected to have EAC atresia according to MRI and 21 ears were ultimately confirmed to have EAC atresia. The accuracy of MRI in diagnosing microtia and EAC atresia was 93.68% and 93.10%, respectively. CONCLUSION: MRI shows good performance in diagnosing fetal microtia and has the potential to evaluate its severity on the basis of classification and EAC status. CLINICAL RELEVANCE STATEMENT: This study was aimed at investigating the role of MRI in the diagnosis and classification of fetal microtia. MRI shows good performance and can help evaluate microtia severity and EAC atresia, thus allowing for better clinical management. KEY POINTS: • MRI is a useful adjunct to prenatal ultrasound. • MRI has a higher accuracy rate than ultrasound in diagnosing fetal microtia. • The accurate classification of fetal microtia and the diagnosis of external auditory canal atresia through MRI may help guide clinical management. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00330-023-09816-5.