Background: Even the healthiest infants undergo painful procedures as part of universal medical care. Untreated early pain is associated with heightened pain response during later procedures in infancy and alteration in response to pain in childhood. Oral sucrose is currently considered the standard of care for acute pain relief in infants. Compelling evidence from 57 randomized controlled trials suggests that oral sucrose reduces bio-behavioral pain response. However, recent data examining the influence of oral sucrose on pain-specific brain activity measured using electroencephalogram (EEG) questions the efficacy of this intervention for reducing pain in the infant brain. Evidence supports the effectiveness of breastfeeding as a pain relieving intervention, however, no studies to date have examined the effect of breastfeeding on pain-specific activity in the newborn brain.

Aims: The primary aim of this study is to examine the influence of breastfeeding in comparison to oral sucrose on pain-specific activity in the newborn brain during a heel lance. The secondary aim will be to determine if there is convergence among outcome measures in either of the intervention conditions.

Methods: Utilizing a single blind, randomized controlled trial design, 126 healthy term infants will be recruited within the first two days of life. Infants will be randomized to have a medically indicated heel lance completed in one of two possible conditions: 1) breastfeeding (n = 63) or 2) sucrose in an infant cot (n = 63). Infants will not be eligible for study participation if they show signs of lower limb tissue damage, have had previous surgery or intraventricular hemorrhage, are born to opioid using mothers or with significant genetic disorders, are unable to breastfeed, or have contraindications to sucrose administration. Pain-specific brain activity will be recorded on EEG for the duration of the blood collection. Infant facial response will be video recorded, and heart rate and oxygen saturation will be measured for calculation of Premature Infant Pain Profile-Revised (PIPP-R) Score, a reliable and valid bio-behavioral measure of pain in infants' 26-44 weeks gestational age. For infants randomized to the breastfeeding condition, data collection will begin with recording of a one-minute baseline (BL1). Following this, a non-painful control stimulus will be applied to the infant's foot to capture a baseline response on EEG to a non-painful event. The infant will then be transferred to the mother and active breastfeeding will be facilitated. A second baseline (BL2) will be recorded prior to heel lance. Pain response will be recorded from the initiation of the heel lance until procedure completion. In the sucrose condition, all monitoring will take place while the infant is in a cot (considered standard of care). Procedures will be consistent with those outlined above with the exception of administration of 24% oral sucrose two minutes prior to the heel lance. Analysis and inference will be calculated based on the intention-to-treat principle. Data from the EEG recording will be grouped into basic waveforms using principal component analysis. Two one-way analysis of variances will be used to assess the effect of stimulation type (non-painful control, painful heel lance) and treatment (24% oral sucrose, breastfeeding) on the principal components. To assess for the effect of treatment on PIPP-R score, group means will be compared using unpaired Student's t-tests.

Hypotheses: Infants in the breastfeeding condition will demonstrate both lower pain-specific brain response and lower bio-behavioral pain scores than infants in the sucrose condition.

Significance: This will be the first study to examine the effect of breastfeeding on pain-specific brain response in infants. In light of the negative consequences of unmanaged pain in infants, it is imperative that effective pain relieving interventions are utilized. Given recent evidence questioning the analgesic properties of sucrose, findings will have important implications for informing optimal pain management practices in infants.

Inclusion Criteria:

• Healthy, full term, normally breastfeeding infants, whose mother is willing to breastfeed during the painful procedure and consents to study participation. Normally breastfeeding infants will be defined as those infants who had fed directly at the breast a minimum of two times in the 24-hours prior to blood collection and whose mother and/or staff nurse reported active sucking and swallowing during those feeds. Infants who have undergone repeated heel lancing for blood glucose and/or bilirubin monitoring (e.g., small or large for gestational age infants, infants born to diabetic mothers, or with hyperbilirubinemia) will be considered eligible, however, diagnosis and the number of prior painful procedures will be recorded and retained for statistical analysis.

Exclusion Criteria:

• Infants will not be eligible for study participation if they are a twin birth (including all classifications of monozygotic and dizygotic twins) due to the potential for non-independence of outcomes between twin pairs, show signs of infection, significant lower limb tissue damage, have had previous surgery or intra-ventricular hemorrhage, are born to opioid using mothers or with significant genetic disorders, are unable to breastfeed or have contraindications to sucrose administration, or whose parents are unable to provide written informed consent.

Two research assistants (RA1, RA2) who are blinded to the intervention condition will be hired to complete facial coding and calculation of infant PIPP-R scores. Each research assistant will only code data for infants in the breastfeeding condition (RA1) or the sucrose condition (RA2) and will not be aware of whether they are watching infant responses to noxious or non-noxious stimulation. To minimize observer bias, research assistants will not be informed of the study design, will not be permitted to attend data collection sessions, and will not share datasets or communicate with the other research assistant regarding the study. During data collection, up close video recording of only the infants face will be completed to attempt to keep coders blind to the nature of the intervention.