RESUMEN
The sonographic findings in four fetuses presenting with ventriculomegaly at first-trimester ultrasound that were subsequently diagnosed as having agenesis of the corpus callosum (ACC) are described. The diagnosis of early ventriculomegaly was suspected subjectively by identification of increased cerebrospinal fluid within the lateral ventricles and confirmed by measuring choroid plexus-to-lateral ventricle length and area ratios. Subsequent scans revealed complete ACC in two cases and partial ACC in the other two. This report adds to the increasing evidence suggesting that first-trimester ventriculomegaly is a strong sonographic marker of underlying brain anomalies, including less evident malformations such as ACC. Detailed second-trimester fetal neurosonography in those women continuing their pregnancies should be performed.