The calming effect of a familiar odor on full-term newborns

We assessed the effectiveness of an odor (familiar or unfamiliar) in soothing healthy full-term newborns undergoing a routine heel stick. Forty-four breast-fed newborns were randomly assigned to one of four groups: Before the heel stick, Group 1 was naturally familiarized with their mother's milk odor, Group 2 was familiarized with a vanilla smell, and Groups 3 and 4 did not receive any familiarization. During and after the heel stick, Group 1 was presented with their mother's milk odor, Group 2 was presented with the familiar vanilla, Group 3 was presented with an unfamiliar odor, and Group 4 was a control group. Infants' crying, grimacing, and head movements were analyzed before, during, and after the heel stick. Results show that infants who smelled a familiar odor (their mother's milk or vanilla) cried and grimaced significantly less during the recovery phase compared with the heel stick phase. Infants who were presented with an unfamiliar odor or no odor showed no significant changes during recovery. Moreover, infants who smelled their mother's milk exhibited significantly less motor agitation during the heel stick compared with the other groups. These findings indicate that smelling a familiar odor reduces agitation during the heel stick and diminishes distress after the procedure.