Neonatal Intensive Care Units (NICU) are environments with a high level of sensory stress. Medical advances and technology have contributed to increase the ratio of survival of premature infants but some devices and practices expose these babies to excessive noise and toxic sensory stimuli for which they are not prepared. This is related to an increase of neonatal morbidities, that are considered as minor sequelae, but that can greatly alter the life of the child and the family. Those responsible for hospital management and caregivers who want to take a step forward, need standards to guarantee the benefit of neonatal health and a proper physical and cognitive development of these babies. Design activity, from a Human-Centered Design approach (HCD), together with Developmental Centered Care (DC) contribute to identify and reduce adverse environmental conditions for newborns and premature infants. The purpose of this paper is to establish a method to provide design recommendations and good practice guidelines from evidence and especially from in-situ observations carried out in neonatal units by a multidisciplinary team (i.e., nurses, NICU supervisors and designers). Thus, we identify proposals to reduce stress situations and obtain potential benefits in the development of the hospitalized infant through adaptation of the NICU macroenvironment (i.e. the reduction of light and noise).