Diagnosing perinatal insults is still primarily based on adequate documentation of general medical and obstetric data, as well as radiological and laboratory results. The measurement of brain constituents, such as S100B protein, may be an alternative and a direct indicator of cell damage in the central nervous system when clinical and laboratory results remain unclear to the end. The purpose of this research is to determine the kinetics of S100B protein in the biological fluids at an early stage of a circulatory disorder. This research is based on a prospective longitudinal study that involved 119 infants, of which the investigated group included 71 risk newborns hospitalized at the Clinic for Children's Diseases - Department of Intensive Care and Treatment and Department of Neonatology - Skopje, from the maternity hospitals at the Gynecology and Obstetrics Clinic - Skopje and the Public Health Institute Gynecology and Obstetrics - Cair, Skopje, while the control group included 48 healthy newborns from the same maternity hospitals.