Maternal singing sustains preterm hospitalized newborns' autonomic nervous system maturation: an RCT

Abstract

Background: Premature birth is known to affect the newborn's autonomic nervous system (ANS) maturation, with potential short and long-term impact on their neurobehavioral development. The purpose of the study was to investigate the effects of maternal directed singing and speaking on the preterm infants' autonomic nervous system (ANS) maturation as measured by the heart rate variability (HRV) parameters.

Methods: In this multi-center randomized clinical trial, 30 stable preterm infants (m = 29,6 weeks of gestational age), without any abnormalities were randomized into an intervention (16) or a control group (14). HRV was measured weekly, for a total of 80 recordings during hospitalization, as well as before and after each session of singing or speaking.

Results: The intervention group showed a significant increase of the percentage value of HRV power in the high frequency range when compared to the control group (p = 0.044). More specifically, the maternal singing significantly increased the high frequency power and decreased the low/high frequency power ratio (p = 0.037).

Conclusions: The preterm infant's vagal activity significantly increased in the intervention group, potentially enhancing their ANS maturation. The effect is specifically evidenced in the singing condition.

Impact: Maternal singing affects the autonomic nervous system maturation of preterm hospitalized newborns in the NICU. No previous studies investigated how early vocal parental intervention can affect preterm infants developement, throught their autonomic nervous system maturation. Early Vocal Contact as an early intervention involving parents has a positive impact on preterm infant's development and it can be easily implemented in the care of preterm infants.

Trial registration: NCT04759573, retrospectively registered, 17 February 2021.

Fig. 1. Boxplots of HF power % values computed during the singing and control conditions, after subtraction of the corresponding values obtained during the first baseline period.

The p-value related to the Mann–Whitney non-parametric test is reported on the top. HF high frequency.

Fig. 2. Boxplots and condition-wise statistics for LF power %, LF power n.u., HF power n.u., and LF/HF computed from the HRV signals of the intervention group.

The p-values of the Friedman statistical test is reported next to the name of each HRV feature. The black orizontal arrow indicates a p-value < 0.05 of the Wilcoxon signed-rank test applied to the corresponding pair of experimental conditions, after Bonferroni correction. LF low frequency, HF high frequency, n.u.: normalized index, LF/HF low/high frequency ratio.