Our technical ability to diagnose fetal anomalies of the central nervous system by ultrasonography and by fetal magnetic resonance imaging far exceeds our current knowledge of their possible neurodevelopmental implications later in life. This limitation often makes obstetric and clinical decisions very difficult. We retrospectively reviewed the ultrasonographic records of 6220 women who had been followed up at two large medical centers between 1994 and 1999. One hundred and sixty (2.6%) women had abnormal fetal central nervous system findings. The neurodevelopmental outcome of these children was assessed by a telephone interview with the parents. Small cerebellar size was the most frequent anomaly, followed by isolated mild ventriculomegaly and isolated choroid plexus pathology. Suboptimal neurodevelopmental outcome was found in 24% of children with isolated ventriculomegaly and in 9% with choroid plexus pathology. In the group of children with a "small cerebellum," suboptimal neurodevelopment was found in 19%. The measurement of transcerebellar diameter in respect to its developmental implication is, to our knowledge, described here for the first time. We believe that cerebellar measurements and their possible neurocognitive implications should be an integral part of future studies. ( J Child Neurol 2004;19:435-438).