Aim While antenatal ventriculomegaly is common, it varies in severity and outcome, with sparse UK data. The authors aim to define the incidence, associated abnormalities and infant outcome for a UK cohort.

Methods All cases of antenatally detected ventriculomegaly attending a single regional fetal medicine unit from May 2001 to October 2008 were entered prospectively onto a database. Ventriculomegaly was defined as mild (10–12 mm), moderate (12–15 mm) or severe (>15 mm) by ultrasonography (coronal slice at the level of the atria). Progressive ventriculomegaly was defined as an increase in the diameter >2 mm, regressed as a reduction >2 mm and stable as a change of <2 mm. Coexistent anomalies, investigations and pregnancy outcome were analysed, and where available infant records at age 6/12 were obtained.

Results A total of 210 cases were identified, giving an incidence of 1.5 cases per 1000 live births in South Wales. Among these, 36% were isolated and 64% non-isolated. Ventricular dilatation was mild in 95/197 (48%), moderate in 38 (19%) and severe in 64 (33%). Seventy per cent of mild cases were isolated. Severity was significantly associated with associated anomalies (p<0.0001). Twenty-seven per cent of mild cases underwent termination of pregnancy. Of 108 cases with consecutive data, mild cases were more likely to regress or remain stable than moderate/severe cases (p<0.0001). There were 89 live births, of whom 48% were mild, 24% moderate and 15% severe. Postnatal details were available on 48 children, 15 (31%) of whom were normal. Among the 34 with postnatal abnormalities, 11 had mild ventriculomegaly, 3 moderate and 20 severe.

Conclusion With an incidence of 1.5/1000 live births in this UK cohort, ventriculomegaly is a common antenatal abnormality. Clearly, regressive cases are more likely to be mild, isolated and have a normal outcome than progressive cases. The positive outcome for mild cases in this series raises the question as to the appropriateness of a 10-mm cutoff. A prospective study with detailed paediatric follow-up is required to define optimal cutoff values and allow appropriate counselling.