: The new scientific knowledge about the behaviour of the newborn and their interactions as a developing factor, as well as the new neurosciences findings about the initial brain formation, gave us several elements for a new vision and reflection about the perinatal routines in hospitals. This study raises questions about the first experiences of the rooming in newborns during the specific act of bath, as the only determining factor in altering both behaviour and physiology. Through the monitoring of the heart rate frequency and observing the changes in the states of consciousness level, this article shows how the type of bath that the newborn is subjected to influences his/her organisation. The study showed significant results in the parameters observed during the electric shower bath, leading to unbalance of the subsystems where the individuals organise themselves; such findings made us classify this procedure as very stressing to the baby. To the contrary the bath in the "Tummy Tub" presented insignificant changes, showing a relaxed baby with normal bath behaviours and physiological status; thus this procedure appears to contribute to an energetic and interactive balance of the baby's various systems. The aggressive approach (electric shower) does not allow the newborn auto-regulation to occur and to get proper stimulation and learn basic interactive responses which would facilitate his /her healthy early infancy development.