Abstract: Objective: To investigate the effects of audio stimulation by maternal heart sound and voice verses music therapy on the overall physical development of premature infants in the Neonatal Intensive Care Unit (NICU). Methods: A total of 90 premature infants who met the inclusion and exclusion criteria were randomly and equally divided into three groups: control group (n=30), music therapy group (n=30) and maternal heart sound and voice stimulation group (n=30). Infants in the control group received routine neonatal care, and those in the music therapy group received music therapy in addition to routine care. Premature infants in the maternal heart sound and voice stimulation group received routine neonatal care, and they were also stimulated by the maternal heart sounds along with mother's voice twice a day for a period of 14 days. At the 7th and 14th day of the intervention, the physical development index, physical growth rate, milk intake and the recovery time to the original birth weight were collected and compared among the three groups. Results: There were no significant differences in terms of infants' body length, head circumference and upper arm circumference among the three groups before and after intervention (P>0.05), and no significant difference was identified in terms of their weight at birth (P>0.05). After 7 and 14 days of intervention, the body weight of premature infants in the group with maternal heart sound and voice stimulation was significantly higher than that in the other two groups (P<0.05), and infants' weight in the music therapy group was significantly higher than that in the control group (P<0.05). The weight growth rate of premature infants in the maternal heart sound and voice stimulation group was also significantly greater than that in the other two groups (P<0.05), with the weight growth rate of infants in the music therapy group being greater than that in the control group (P<0.05). There were no significant differences in terms of the body length, head circumference and upper arm circumference growth rate among premature infants in the three groups (P>0.05). In addition, the average daily milk intake in the first week was no different among premature infants in three groups (P>0.05), however, the daily milk intake during the second week in infants with maternal heart sound and voice stimulation was significantly greater than that of the infants in the music therapy group and control group (P<0.05). Infants in the maternal heart sound and voice stimulation group recovered to birth weight significantly faster than those in the music therapy group and the control group (P<0.05), and with the recovery time in infants in the music therapy group being shorter than that of the control group (P<0.05). Conclusion: Compared with music therapy, maternal heart sound combined with voice stimulation can increase premature infants' milk intake during hospitalization, shorten the time needed to recover to their initial birth weight, and increase the weight growth rate, therefore promote overall physical development of premature infants.

Key words: premature infant; maternal sound stimulation; music therapy; physical development