Fetal Ventriculomegaly Across the Severity Spectrum: Prenatal Ultrasound Features, Longitudinal Evolution, and Additional Fetal MRI Findings

Background/Objectives: Fetal ventriculomegaly is a heterogeneous prenatal finding with variable severity, evolution, and risk of associated cerebral abnormalities. Prenatal ultrasound is the primary diagnostic and follow-up modality, while fetal magnetic resonance imaging (MRI) may provide additional anatomical information. This study evaluated ultrasound features and longitudinal evolution across the ventriculomegaly severity spectrum and investigated prenatal features associated with additional MRI abnormalities. Methods: This single-center observational cohort included 62 fetuses who underwent detailed prenatal ultrasound, fetal MRI, and serial ultrasound follow-up. Ventriculomegaly was classified as mild (10–12 mm), moderate (>12–15 mm), or severe (>15 mm). Multivariable logistic regression assessed prenatal features associated with additional MRI abnormalities, and receiver operating characteristic analysis evaluated its discriminatory performance. Results: Mild, moderate, and severe ventriculomegaly were present in 12 (19.4%), 22 (35.5%), and 28 (45.2%) fetuses. Additional MRI abnormalities increased with severity (16.7%, 40.9%, and 71.4%; p = 0.004). Longitudinal evolution differed across severity groups (Fisher’s exact test, p = 0.013), with progression observed in 25.0%, 45.5%, and 71.4% of mild, moderate, and severe cases, respectively. Greater ultrasound ventricular diameter (OR 1.19 per 1 mm increase, 95% CI 1.03–1.37; p = 0.021) and bilateral asymmetric ventriculomegaly (OR 3.82, 95% CI 1.04–13.96; p = 0.043) were independently associated with additional MRI abnormalities. Ventricular diameter showed moderate discriminatory performance (AUC 0.768, 95% CI 0.651–0.886); an exploratory, data-derived 13.5 mm threshold yielded 83.9% sensitivity and 54.8% specificity. Conclusions: Increasing ventricular severity was associated with more frequent progression and additional MRI abnormalities. The associations of ventricular diameter and bilateral asymmetric ventriculomegaly with additional MRI abnormalities should be considered exploratory and require further validation. The identification of additional abnormalities even in mild cases supports the complementary role of fetal MRI alongside longitudinal ultrasound assessment.