Introduction The definition of borderline cerebral lateral ventriculomegaly (VMG) is an atrial width of 10-15 mm on the transverse plane at 15-40 weeks' gestation. The aim of this study was to evaluate the prognosis of borderline ventriculomegaly cases through a diagnostic path and a postnatal follow-up. Materials and Methods A retrospective study considering 59 single pregnancy women between 19-36 weeks' gestation that were referred to our prenatal diagnosis division with a diagnosis of borderline VMG (atrial width 10-15 mm) at the first ultrasound observation. All babies born with borderline VMG had a transfontanellar scan at 48 hours and 3 months after delivery. Results Patients with isolated borderline VMG (n=42) showed no progression in numeric values at serial evaluations after first observation. In 10 cases (20%) fetal RM was necessary for the presence of associated anomalies. Three cases presented bilateral progressive symmetric VMG and caesarean section was performed between 34 and the 35 weeks due to Doppler anomalies associated with IUGR. One case presented a primary CMV infection with intracranial haemorrhage and fetal death at 27 weeks. Four cases presented an asymmetrical bilateral dilation with discrepancy ≤3mm. Three patients in this group were lost to follow-up and not considered for final data evaluation. One patient delivered at 32 weeks for PROM and the baby presented cerebral injury due to hypoxia linked to prematurity. Discussion In monolateral VMG with borderline isolated dimensions up to 11.2 mm, the prognosis should not be considered as the one expected for a normal lateral ventricular width baby. In the presence of borderline isolated VMG is important to consider a counselling prognostic reassuring without ignoring information of possible, although rare, possibility of delayed occurrence of anomalies and the associated risk of psicomotory delay, although generally mild/moderate (2-4%).