The impact of parental singing on neural speech sound processing in preterm infants, maternal wellbeing, and early relationship after preterm birth : implications for practice in neonatal care

The present thesis aimed to examine the impact of parental singing during kangaroo care on neural speech sound discrimination in preterm infants, maternal wellbeing, and early mother-infant relationship after preterm birth. The aim was also to create a working model for music therapists in the neonatal wards that focuses on educating parents of preterm infants about the importance of using parental voice after preterm birth. This thesis consists of four studies. Studies I (n = 192) and II (n = 40) served as background research for Study III. They aimed to provide information about sound processing in healthy full-term-born infants and compare auditory discrimination between full-term infants and preterm infants receiving standard care. Study III (n = 40) investigated the effects of parental singing on neural speech sound processing in preterm infants. Study IV (n = 36) examined the effects of singing on maternal anxiety, wellbeing, and early mother-infant relationship. The data for Studies III and IV were collected within the Singing Kangaroo cluster-randomized controlled trial. In this study, a certified music therapist motivated and supported parents in the intervention group to sing during daily kangaroo care, whereas parents in the control group conducted standard kangaroo care without guidance from the music therapist regarding singing. In both groups, parents conducted kangaroo care during the gestational weeks 33–40 and reported the duration of daily care in diaries. Parents in the intervention group also reported the daily singing duration and control group parents described the auditory environment of each kangaroo care situation. After the study period, the infants’ auditory event-related potentials to speech sound and pure tone changes were measured using electroencephalography. The measurements were also conducted with full-term newborns in Studies I and II. Maternal anxiety was measured in both groups using the State-Trait Anxiety Inventory questionnaire at the beginning and the end of the study period. Intervention group mothers also filled up a self-report questionnaire concerning their singing experiences after preterm birth. The results of Studies I and II showed that the full-term infants had statistically significant brain responses mainly to the acoustically distinct speech sounds. Study II further revealed that the processing of speech sound changes did not differ between the full-term and preterm infant groups. According to the results of Study III, preterm infants in the singing intervention group had larger brain responses to speech sound changes when compared to the preterm infants in the control group whose parents did not sing. Furthermore, improved neural speech sound processing was associated with the overall duration of the intervention in the singing group of preterm infants. Thus, the longer the singing intervention was, the larger brain responses were elicited to speech sound changes in the intervention group. In Study IV, maternal anxiety was reduced in the singing intervention group after the study period when compared to the control group. The mothers in the singing group experienced that singing was relaxing for the infants and themselves and it had a positive impact on their mood and overall wellbeing. The mothers also reported that singing supported early relationship by creating interaction moments and enhancing emotional connection. The intervention group mothers benefitted from the support and guidance they received from the music therapist during hospital care. All the mothers in the intervention group continued singing after the study period and it became an important part of their everyday life and interaction after discharge from the hospital. The main results of this thesis indicate that repeated parental singing during kangaroo care may improve speech sound discrimination in preterm infants at term age. Furthermore, singing during kangaroo care may reduce maternal anxiety, relax both infants and mothers and support their early relationship by adding interaction moments and an emotional component to the care situation. Mothers can benefit from support and guidance from a music therapist after preterm birth and it may have a long-term impact on their musical behavior. According to the results of the current thesis, daily singing routines can be recommended for parents after preterm birth to support the development of the auditory system and neural speech sound processing in preterm infants, maternal wellbeing, and the development of mutual relationship. This is a non-invasive and feasible way for all families to support wellbeing and early interaction and it could be introduced more in general in the care of both healthy and sick infants. Based on the results and conclusions of this thesis and literature, a working model proposal for music therapists is introduced at the end of this work. The model focuses on educating parents of preterm infants about the importance of using parental voice after preterm birth to support their infants’ development, their own wellbeing, and early relationship.