Objective To explore the value of prenatal ultrasound quantification of ventricular dilation on guiding neonatal neurodevelopment evaluation and prognosis. Methods The clinical data of 98 pregnant women with fetal lateral ventricular dilatation during prenatal examination in our hospital from January 2021 to December 2022 were selected and the women were included in dilatation group. The clinical data of 98 pregnant women with normal fetal lateral ventricle during prenatal examination were selected and the women were enrolled as normal group. Prenatal ultrasound indicators [lateral ventricle width, longitudinal diameter of third ventricle (CD), maximum interthalamic adhesive diameter (ITAD)] and neonatal neurodevelopment status [neonatal neurobehavioral assessment (NBNA) score, Gesell developmental scale] were compared between the two groups of neonates. The diagnostic efficiency of prenatal lateral ventricle width, CD and ITAD on neonatal ventricular dilatation was evaluated by receiver operating characteristic (ROC) curve. According to the severity of lateral ventricular dilatation, the women in dilatation group were divided into mild group and severe group, and the neonatal lateral ventricle width, CD, ITAD, NBNA score and Gesell score were compared. The relationship between prenatal lateral ventricle width, CD, ITAD and NBNA score and Gesell score in neonates with lateral ventricular dilatation was evaluated by pearson correlation coefficient. Results The lateral ventricle width and CD in dilatation group were higher than those in normal group while the ITAD and NBNA score were lower than those in normal group (all P<0.05). Lateral ventricle width, CD and ITAD had high diagnostic efficiency on ventricular dilatation. Lateral ventricle width had the highest diagnostic efficiency, with AUC of 0.907, sensitivity of 92.86% and specificity of 76.53% (all P<0.05). The lateral ventricle width and CD in severe group were higher while the ITAD, NBNA score, Gesell score and gestational age were lower compared with those in moderate group and mild group (all P<0.05). The lateral ventricle width and CD were negatively correlated with NBNA score, while ITAD was positively correlated with NBNA score (all P<0.05). There was a statistical significance in the prognosis aspect among neonates with different degrees of lateral ventricular dilatation (P<0.05). Conclusion Prenatal ultrasound examination can effectively diagnose neonatal lateral ventricular dilatation and its severity, and it is of great significance for improving fetal prognosis.