ABSTRACT
Timing of examination. Ultrasound screening for fetal brain malformations is performed at 19-22 weeks’ gestation. For the assessment of the fetal brain, the 2nd trimester anomaly screening scan includes the following axial planes: transthalamic, transventricular, and transcerebellar.1-3
This has become the standard approach. However, major developmental events occur in the second half of the gestational period, including neuronal proliferation, migration and organization; and the same is true for acquired lesions, such as hemorrhage and tumors, which usually occur late in gestation. Therefore, although it is possible to detect most fetal brain anomalies in the 2nd trimester, migration, proliferation and organization4,5 disorders as well as acquired lesions can become apparent only in the 3rd trimester.
