ABSTRACT
The application of three- and four-dimensional (3D and 4D) sonography in the investigations of embryonic and fetal activities in the natural environment has produced invaluable information on the development of fetal behavior and has therefore provided direct insight into the prenatal functional development of the central nervous system (CNS). It has been shown that all of the movement patterns of a newborn originate from the prenatal period. The onset and developmental course of the movement patterns have been studied extensively, and the interpretation of those results together with information on the structural development of the fetal brain and other organ systems has demonstrated that fetal motility reflects the maturation of the fetal CNS. 1 Furthermore, it has been shown that fetal motility is not only required for the maturation of motor functions but is also involved in the development of other organs, such as the lungs. Prenatal observation of specific reflexive behavioral patterns such as fetal yawning has given a new perspective on the purpose of this reflex. Although the characteristics of yawning in adult age have been described in detail, its role is still poorly understood. The presence of spontaneous yawning movements from the early 2nd trimester of gestation onwards indicates its evolutionary importance. Therefore, the investigation of prenatal yawning patterns could improve our understanding of the physiologic role of this reflex. On the other hand, an altered frequency of yawning has been observed in adults in relation to various brain dysfunctions, which leads to the assumption that such a relation might exist in the fetal period as well, and could be one of the indicators of brain function disturbances.
