<prompt> Most common cause of fetal ventriculomegaly is ?Arnold Chiari malformationIArnold Chiari malformationIIAqueductal stenosisDandy Walker malformation  <response>: Hydrocephalus is characterized by an increased CSF volume with progressive ventricular dilatation ventriculomegaly.Obstructive or noncommunicating hydrocephalusventriculomegaly develops most commonly in children because of an abnormality of the aqueduct or a lesion in the 4th ventricle.Obstruction of the aqueduct is the single most common cause of fetal and neonatal hydrocephalus ventriculomegaly.Non obstructive or communicating hydrocephalus most commonly follows a subarachnoid hemorrhage, which is usually a result of intraventricular hemorrhage in a premature infant. 