Central nervous system (CNS) malformations play a relevant role in the set of all fetal malformations, standing out for the following factors: • incidence: this is the second highest after cardiac malformations; • feasibility of prenatal diagnosis: currently, they are the most frequently diagnosed malformations, together with urinary tract malformations; • difficulty in evaluating the patient’s prognosis: many times, a multidisciplinary discussion is required to define the prognosis. Ultrasonography (US) is the best screening method to identify fetal CNS malformations(1). The echographic study of the cephalic pole at the 12th gestational week already constitutes a relevant biometric method for evaluating the gestational age. It also provides an early morphological appreciation of the development of the brain and of the fetus as a whole, together with other parameters, such as fetal dynamics (tonus, respiratory motion, heartbeats) and structural elements of the fetus (spine, skeleton, face, thorax and abdomen)(1). A good echographic study depends on several factors, such as positioning, fetal mobility and growth, volume of amniotic fluid, position of the placenta, maternal wall, quality of the apparatus, and the sonographer’s experience. Three-dimensional US (3DUS) has become an integral part in the assessment of a great number of fetal abnormalities. As conventional US and 3DUS are compared in the evaluation of medullary canal malformations, multiplanar 3DUS imaging provides more complete information on such alterations. Among others, the following benefits from this imaging modality are highlighted: