Evaluation of the fetal central nervous system is an important aspect of first trimester ultrasound because some major anomalies can be easily identified and thus provide sufficient information to advise parents on pregnancy monitoring, fetal treatment options, and postnatal management and prognosis. Therefore, prenatal evaluation of the fetal central nervous system is of utmost importance with fetal neurosonography as the mainstay.

Because congenital central nervous system malformations are the most common group of fetal malformations, second only to cardiac malformations, fetal head ultrasound in the second trimester remains an important screening tool for early detection of fetal abnormalities. Subsequently, fetal head ultrasound is indicated in the third trimester to assess the degree of malformations as well as to plan for safe birth and subsequent treatment options.