The effect of inhaling mother's breast milk odor on the behavioral responses to pain caused by hepatitis B vaccine in preterm infants: a randomized clinical trial

Background: Nowadays, it is generally assumed that non-pharmacologic pain relief in preterm infants is an important measure to consider. Research findings suggest that familiar odors have soothing effects for neonates. The aim of this study was to compare the effect of maternal breast milk odor (MBMO) with that of another mother's breast milk odor (BMO) on the behavioral responses to pain caused by hepatitis B (HB) vaccine injection in preterm infants. Methods: This single-blind randomized clinical trial was performed over the period between February 2019 and March 2020 in the neonatal intensive care unit of Babol Rouhani Hospital, Iran. Ninety preterm infants, who were supposed to receive their HB vaccine, were randomly assigned into three groups: MBMO (A), another mother's BMO (B), and control with distilled water(C). Oxygen saturation (SaO2), blood pressure (BP) and heart rate (HR) were recorded for all participants through electronic monitoring. In addition, premature infant pain profiles (PIPP) were determined through video recording for all three groups during intervention. The chi-square, ANOVA and ANCOVA were used for analyzing the data, and P < 0.05 was considered significant in this study. Results: No significant differences were found between the three groups in mean +/- SD of HR, BP, and Sao2 before the intervention (P > 0.05). After the intervention, however, the means for heart rate in groups A, B, and C were 146 +/- 14.3, 153 +/- 17.5 and 155 +/- 17.7, respectively (P = 0.012). Moreover, the means for PIPP scores in groups A, B and C were 6.6 +/- 1.3, 10 +/- 2, and 11.4 +/- 1.9, respectively (P < 0.001). There was no significant difference found between groups in their means of SaO2, systolic and diastolic blood pressure after the intervention (P > 0.05). Conclusions: The results indicate that stimulation with MBMO is effective in reducing pain in preterm infants; therefore, it can be postulated that this technique can be considered in less invasive procedures such as needling.

Automated summary

The study findings suggest that stimulation with maternal breast milk odor can effectively reduce pain in preterm infants, indicating its potential use in less invasive procedures.