INTRODUCTION: The liver is the central organ of metabolic activity in the body.
 OBJECTIVES: The purpose of this study was to determine predictors, major clinical features, and laboratory criteria for the severity of disorders of the functional state of the hepatobiliary system in newborns with neonatal jaundice (NJ). The study included 164 full-term infants. The main group - 92 children, with manifestations of pathological jaundice, was divided into two subgroups, depending on the severity of the pathology, considering concomitant perinatal pathology. IA group (46 children) includes children, condition of which was defined as moderate, IB (46 children) – children, condition of which was defined as severe, the control group consisted of 72 healthy term infants.
 METHODS: The complex of examination methods includes: collection of anamnesis of antenatal and perinatal periods in the mother, clinical examination of the newborn and laboratory methods of examination: blood biochemical analysis (TSB blood, bilirubin fractions, activity of ALT enzymes, AST, ALP , γ-GT, glucose level of blood serum, cholesterol, triglycerides) ultrasound examination of infants' liver.
 RESULTS: Clinical symptoms that confirmed the functional impairment of the hepatobiliary system (HBS) in newborns who had signs of NJ in perinatal pathology are: hepatosplenomegaly, impaired bowel function, hypoglycemia, anemic syndrome, hemorrhagic disorders. The results of biochemical studies of the blood showed an increase in the severity of the pathology, an increase in the level of TSB and the fraction of indirect bilirubin, activation of the cytolysis markers of ALT and AST, increase of LDH activity, decrease in the activity of g-GT and ALP, as well as decrease in the level of total protein, albumin, glucose, increase in the level of urea, cholesterol and triglycerides. The most explicit manifestations of HBS dysfunction were found in newborns with a severe condition at birth and in the early neonatal period caused both by the NJ and other comorbidities. Taking into account the revealed deepening of biochemical changes in indicators of blood serum in correlation with the increase of clinical manifestations of pathology, the diagnosis of changes in the early stages will allow to diagnose in time the disorders of the functional state of HBS in NJ for the purpose of appropriate therapeutic correction.
 CONCLUSION: The results of the analysis of anamnestic and clinical-laboratory parameters in newborns with NJ showed on the background of a clinical signs of dysfunction of the hepatobiliary system, the presence of significant biochemical changes, especially enzymatic activity, including, ALT, AST, LDH, ALP, and g-GT and, also an increase in TBS levels and an indirect bilirubin fraction, a decrease in total protein and albumin, glucose, a rise in urea, cholesterol and triglycerides.
 The use of a biochemical markers in newborns with clinical manifestations of neonatal jaundice, especially in cases of significant severity of the condition with concomitant perinatal pathology, requires more detailed analysis in order to determine the main pathogenesis of disorders of the functional state of the hepatobiliary system for the purpose of timely correction and improvement of the outcome of treatment.