The fetal life stimulated strong interest even from ancient time; pioneeristic research in XIX century led to particularly important statements in front of the reduced means of inquiry. Thanks to the introduction of ecography we could observe the fetal life, in parallel with neurophysiological and electroencephalographic research, particularly the fetal expressivity; that allow us to speak of a "fetal personality" from the 14th week. The article presents a preliminary study on three couple of non identical twins, from the 12th week to the birth, through monthly ecographic sessions and then from the birth to 2 years through the Infant Observation method. This study revealed that it is possible to recognize a specific personality to each of the subjects observed. Moreover, specific behaviours in the fetal environment resulted to be precursors of very significant attitudes in the post-fetal life. The observational study here illustrated let us to inquiry the meaning of the infant individuality and the environment influence in the fetal life, related to behavioural attitudes in the post-fetal life.