ABSTRACT Purpose: This research was done for the purpose of determining the impact of breast milk smell administered to term infants hospitalized in neonatal intensive care units (NICU) due to physiological jaundice on their bilirubin levels, length of remaining in phototherapy and comfort.

Material and Method: It is an experimental, randomisation, controlled research. Target population of the research consisted of a total of 72 term infants who were hospitalized in the NICU of Bilecik Bozuyuk Public Hospital and met the sample selection criteria. Our research includes two groups. Breast milk smell group and control group. The infants were assigned to the groups via randomization method. Sample assignment to the groups was performed using stratification and blocking methods. The infants meeting the research sample selection criteria were stratified according to their postnatal age and then assigned to each group equally (blocking) by lot. However, two infants in the control group were excluded from the research at the request of their parents as the research continued. Thus, the research was completed with a total of 72 infants; 37 in the breast milk smell group and 35 in the control group. In the research, the data were collected using "Personal Data Collection Form", "Phototherapy Follow-up Chart" and "Neonatal Comfort Behavior Scale". The data were analyzed using the SPSS (Statistical Package for Social Sciences) 21.0 (IBM corp. Relased 2012. IBM SPSS Statistics for Windows, version 21.0 Armonk, NY: IBM corp.) package software.

Inclusion Criteria:

• The term baby (37-39+6 weeks) of the newborn according to the menstruation of the mothers
• Need to have phototherapy treatment for the first time
• Not taking analgesics and/or sedatives in the last 24 hours
• Body weight in the range of 2500 - 4000 g
• Postnatal age of the newborn greater than 48 hours
• Turkish Neonatology Society's approach, follow-up and treatment guideline for neonatal jaundice (2014) Being a medium and high risk baby according to the table of risk status determination of babies according to postnatal age and transcutaneous or total serum bilirubin values.
• Not taking any treatment or medication other than phototherapy treatment
• The mother and/or father accepting the study is having a baby.

Exclusion Criteria:

• Having a health problem other than physiological jaundice
• Findings such as tachypnea, fever
• Having an invasive procedure other than blood sampling once a day for babies
• Exchanged babies
• Babies with Rh and AB0 incompatibility
• Babies with elevated bilirubin levels earlier than 48 hours
• Discord with family