The uniform development of the human embryo, as described by classic human embryology, has been confirmed by sonoembryological studies. In particular, the embryonic brain is suitable for transvaginal ultrasound examination, because the large “cystic” cavities of the brain can easily be imaged. Sonoembryology not only describes normal embryonic anatomy and normal relations and proportions of organs, but also the development of structural abnormalities. Approximately one-third of all congenital anomalies, originate from the central nervous system (CNS). Based on normal sonoembryology and on recent experiences with early CNS anomalies, we recognize some sonographic signs of an early CNS anomaly: (1) Apparent dysmorphology of the brain or the head; (2) Altered appearance of the cerebral ventricles with disproportion of the brain compartments, where the amount of fluid is either greater or less than normal; (3) In the early fetal period, choroid plexuses that are too small to fill the ventricle from the medial to the lateral wall; (4) Irregular contour of the spine/back; (5) Extra-CNS anomalies. In the following survey, normal sonoembryology of the CNS is described, and CNS anomalies of the early pregnancy are discussed.