ABSTRACTBACKGROUND AND OBJECTIVES:This study aimed at evaluating pain of newborns submitted to blood gases analysis by means of the Neonatal Facial Activity Coding scale, as well as at comparing newborns’ physiological parameters before and during arterial puncture.METHODS:This was an exploratory, descriptive and cross-sectional study with 26 newborns submitted to blood gases analysis and admitted to a Neonatal Intensive Care Unit. Data were collected in April and May 2010, by means of an identification form and physiological changes presented by newborns before and during the procedure.RESULTS:There have been newborn facial manifestations of pain (100%), heart rate changes (50%) and decreased oxygen saturation (34.7%).CONCLUSION:When physiological parameters were compared before and during arterial puncture, there have been pain facial manifestations in all newborns as well as physiological changes such as decreased oxygen saturation levels and increased heart rate, according to the Neonatal Facial Activity Coding scale, showing that, although unable to verbalize, newborns are able to show changes expressing the pain felt at arterial puncture. The application of this scale was especially important for favoring sensitization and a holistic nursing care for painful newborns.