Fetal behaviour in early pregnancy.

The emergence of embryonic and fetal movements in the first half of gestation is described. From their emergence onwards movements are specific and easily recognizable and during the course of gestation their appearance hardly changes; they closely resemble movement patterns observed in preterm and full-term newborn infants. Most of the movements described during the course of gestation have already emerged before 16 wk. The quantity of the distinct motor patterns undergoes several changes before 20 wk of gestation. This holds for their incidence and for their temporal sequence. The fact that fetal movements are specific and easily recognizable from their onset onwards makes them useful for assessing the development of the nervous system in normal and abnormal conditions.