Standard Prenatal Ultrasound Markers Associated With MRI ‐Only Central Nervous System Abnormalities in Fetal Ventriculomegaly

Objective To identify standard prenatal ultrasound markers associated with central nervous system abnormalities detected only by fetal MRI in fetuses with ventriculomegaly considered apparently isolated on standard prenatal ultrasound. Methods This retrospective study included 199 singleton pregnancies with fetal ventriculomegaly evaluated by standard prenatal ultrasound and fetal MRI within 72 h. Dedicated fetal neurosonography was not routinely performed. Ventriculomegaly severity was classified according to the maximum lateral ventricular atrial width. Among fetuses without additional central nervous system abnormalities on standard prenatal ultrasound, cases with and without MRI‐only abnormalities were compared. Ultrasound‐based markers were assessed using exploratory logistic regression, and the discriminatory ability of initial ventricular width was evaluated using receiver operating characteristic analysis. Results Among 183 fetuses considered apparently isolated on standard prenatal ultrasound, fetal MRI detected additional central nervous system abnormalities in 19 cases (10.4%). In the exploratory multivariable model, greater ultrasound‐defined ventriculomegaly severity was associated with MRI‐only abnormalities (OR, 2.947; 95% CI, 1.375–6.313), and interval ventricular progression showed a stronger association (OR, 25.217; 95% CI, 6.496–97.895). Initial ventricular width showed exploratory discriminatory ability, with different performance in early‐onset and late‐onset cases. Conclusions In fetuses with ventriculomegaly considered apparently isolated on standard prenatal ultrasound, greater ventriculomegaly severity and interval ventricular progression were associated with additional CNS abnormalities detected by fetal MRI. These findings support risk‐stratified consideration of fetal MRI after standard prenatal ultrasound but should not be extrapolated to fetuses evaluated with dedicated fetal neurosonography. The ventricular‐width thresholds identified in this cohort should be considered exploratory.