Introduction Mild intracranial ventriculomegaly (VM) is a common finding during routine and detailed anomaly scanning. It can be associated with congenital infection, aneuploidy, cerebral vascular insults and additional fetal abnormalities. It can also be of no pathological significance when found in isolation and therefore presents a diagnostic challenge to clinicians. Studies have shown that fetal MRI provides further important information in 6–10% of cases. The authors sought to examine the role of fetal brain MRI in our population.

Methods The authors conducted a retrospective case review of fetal brain MRIs for isolated mild VM since November 2007. The aim was to determine (1) if MRI confirmed US findings, (2) if there were any additional abnormalities seen on MRI and (3) if additional MRI information altered parental counselling.

Results 15 cases with known neonatal/postmortem outcomes fitted the criteria. MRI confirmed VM in 14 cases. No additional brain abnormalities were found on MRI however severe VM was identified in four cases. MRI altered counselling and parental choice in two cases; both opted for termination of pregnancy following reported severe VM on MRI. Postmortem identified a posterior fossa meningeal cyst in one case and an acardiac twin in the other, neither were diagnosed on antenatal US or MRI. Antenatal detection of lobar holoprosencephaly by either modality was missed in one case of mild VM.

Conclusion In our small group of patients, MRI was useful in identifying severe VM in four cases (26%) and changed parental choice in two cases (13%).