AbstractObjectiveTo review the prenatal diagnosis of apparently isolated severe ventriculomegaly (SVM) in a tertiary referral fetal medicine unit and report on perinatal and neurodevelopmental outcomes.MethodsAll cases of isolated SVM referred to Fetal Medicine at the NMH between 2000 and 2008 were identified. Outcome information was obtained from detailed telephone interviews with parents and paediatric records and histopathology in cases of stillborn fetuses.ResultsThirty‐six cases of SVM were referred, out of which 19 were diagnosed with ‘apparently’ isolated SVM. Macrocrania was present in 88% at 36 weeks (mean HC 439 mm). Cephalocentesis was performed in six cases with poor prognosis. All resulted in perinatal loss. The neurodevelopmental outcome of survivors with isolated SVM (ten live‐born survivors) showed major neurological morbidity in 50% (5/10) of the cases, mild morbidity in 40% (4/10) and a normal outcome in only one case.ConclusionIsolated SVM had a very poor perinatal outcome with neurological and physical disability in the overwhelming majority. Only one case of the 17 (6%) diagnosed initially with ‘apparently’ isolated SVM was born alive without handicap. Information from our series may aid couples in decision making about pregnancy interruption and the difficult decision of prenatal or intrapartum cephalocentesis. Copyright © 2009 John Wiley & Sons, Ltd.