Ultrasound of the fetal central nervous system

The diagnosis of fetal anomalies is one of the major reasons that legitimat e an extensive use of ultrasound in pregnancy. Among all fetal anomalies, t hose pertaining to the central nervous system (CNS) occupy a special positi on. With an estimated incidence of one per 100 births [1,2] they are among the most frequent malformations, and they often have a severe prognosis. In many cases they have a genetic background, and as a consequence of this th ere is a large number of couples at specific risk who demand antenatal diag nosis. The CNS was probably the first apparatus to be investigated in utero by diagnostic ultrasound. Anencephaly was the first congenital anomaly to be recognized by this technique before viability [3]. Modern high-resolutio n ultrasound equipment yields a unique potential in evaluating normal and a bnormal anatomy of the fetal neural axis from the very early stages of deve lopment. In this article, the most recent advances in the sonographic inves tigation of the fetal brain and the identification of CNS anomalies will be reviewed.