The Impact of Preterm Infants' Continuous Exposure to Breast Milk Odor on Stress Parameters: A Pilot Study

Objective: This pilot study aimed to assess the effect of continuous exposure to the odor of own mothers' breast milk (BM) on the stress parameters of preterm infants. Materials and Methods: Fifteen healthy preterm infants were included. Mean heart rate and salivary cortisol were measured over three consecutive time periods, each lasting 2 days: (1) preintervention (odor free); (2) intervention, during which a cotton pad soaked with 1.5 mL of BM was placed near the infant's head with the aim of providing continuous exposure to its odor; (3) postintervention period (odor free). Results: Saliva cortisol levels differed significantly between the three exposure periods (pre-, during, and post-BM odor exposure): 11.38 ± 5.03, 9.51 ± 4.38, and 4.99 ± 3.42 nmol/L, respectively. A repeated univariate analysis of the cortisol measure showed a significant difference (F = 9.34; df = 2.28, p < 0.001). There was no difference in mean heart rate over the three study periods. Conclusions: Preterm infants exposed to BM odor from their own mothers demonstrate a persistent decrease in saliva cortisol levels, which continues after termination of the intervention. This finding may suggest that exposure to own mothers' BM odor has a soothing effect on preterm infants. Further randomized controlled studies are needed to evaluate this simple, safe, and inexpensive intervention.