The lateral cerebral ventricle in early second trimester.

In routine imaging of normal early second trimester pregnancies, one will not infrequently encounter potentially confusing cases which may raise the question of fetal hydrocephalus. In a retrospective analysis of 100 cases, this appearance occurred in 10. The anatomic origins of this potential error are discussed, and an imaging technique is described which can be used to exclude fetal hydrocephalus in confusing cases. Close apposition of the normally large choroid plexus with the medial and lateral walls of the ventricular body and atrium indicates normalcy.