Diagnostic Value of Choroid Plexus-to-Lateral Ventricle Volume Ratio (CLVVR) in First-Trimester Screening (11-13⁺

Background: Traditional first-trimester screening for chromosomal abnormalities using nuchal translucency (NT), serum biomarkers, and cell-free DNA-based screening still has limitations, particularly for morphology-based early risk enrichment and for abnormalities outside the main autosomal trisomies. This study evaluated a novel 3D ultrasound marker-the choroid plexus-to-lateral ventricle volume ratio (CLVVR)-for detecting fetal autosomal aneuploidies at 11-13⁺ Methods: In this prospective, case-enriched cohort study, 142 singleton pregnancies (100 euploid and 42 aneuploid) underwent 3D volumetry using Virtual Organ Computer-Aided Analysis (VOCAL). CLVVR was calculated from choroid plexus volume and lateral ventricle volume. Diagnostic performance was assessed using receiver operating characteristic (ROC) analysis and compared with a baseline Fetal Medicine Foundation (FMF)-style screening model and an updated model incorporating CLVVR. Results: CLVVR was significantly lower in trisomy 21 (0.317) and trisomy 18 (0.270) than in euploid fetuses (0.458; P < 0.001), whereas no significant differences were observed in sex chromosome or structural chromosomal abnormalities. CLVVR showed good discriminatory performance for autosomal aneuploidies (AUC = 0.928, sensitivity = 91.0%, specificity = 77.5%) and outperformed choroid plexus volume alone. In the external validation analysis, incorporation of CLVVR improved the AUC of the baseline FMF-style model from 0.927 to 0.959. Intra- and interobserver reproducibility was high (ICC > 0.90). Conclusion: CLVVR appears to be a reproducible, non-invasive morphometric marker for trisomy 21 and trisomy 18 in the first trimester. Its integration into an established screening framework improved discrimination in an external validation analysis, although broader validation is still needed before routine implementation.