Development of an Integrated Deep Learning Approach for Detecting Fetal Brain Abnormalities at Routine Second Trimester US Scan: A Multicenter Study.

Purpose To develop and validate an anatomy-aware, two-stage, end-to-end deep learning pipeline for fetal brain abnormality automated detection on standardized second-trimester brain US images. Materials and Methods This retrospective multicenter study included 319 fetal brain images (218 normal, 101 abnormal) between 19 weeks ± 0 and 23 weeks ± 6 of gestation from nine international fetal medicine centers, each with paired standard transventricular and transcerebellar axial plane images acquired at second-trimester US between January 2010 and December 2022. Abnormalities were confirmed by neonatal imaging or autopsy. Images were annotated for six key brain regions by two experienced fetal medicine specialists. An anatomy-aware, two-stage deep learning pipeline was developed, consisting of a You Only Look Once version 5-based object detector followed by a classification network using a Mini-ResNet feature extractor within a HexaNet architecture. The pipeline classified each image as normal or abnormal. Object detection performance was evaluated using mean average precision at an intersection-over-union threshold of 0.5 (mAP@0.5). Classification performance was assessed using the area under the receiver operating characteristic curve, sensitivity, specificity, and F1 score. Results The object detection model achieved a mAP@0.5 of 0.93 (95% CI: 0.90, 0.96) on the test dataset. The classification model achieved an area under the receiver operating characteristic curve of 0.96 (95% CI: 0.90, 1.00), a sensitivity of 87% (95% CI: 67, 100 [13 of 15]), a specificity of 91% (95% CI: 79, 100 [29 of 32]), and an F1 score of 0.84 (95% CI: 0.67, 0.96) for distinguishing normal from abnormal fetal brain images. Conclusion The developed model achieved high diagnostic performance for the detection of brain anomalies at routine fetal second-trimester US. Keywords: Artificial Intelligence, Machine Learning, Fetal Neurology, Neurosonography, Fetal Brain Malformation, YOLOv5, Neural Networks Supplemental material is available for this article. © RSNA, 2026 See also commentary by Rafful in this issue.