Recorded maternal voice for preterm neonates undergoing heel lance

To determine if a recording of a mother's voice talking soothingly to her baby is useful in diminishing pain in newborns born between 32 and 36 weeks' gestational age (GA) during routine painful procedures.

While maternal skin-to-skin contact has been proven efficacious for diminishing procedural pain in both full-term and preterm neonates, it is often not possible for mothers to be present during a painful procedure. Because auditory development occurs before the third trimester of gestation, it was hypothesized that maternal voice could substitute for maternal presence and be effective in diminishing pain response.

Preterm infants between 32 and 36 weeks' GA (n = 20) in the first 10 days of life admitted to 2 urban university-affiliated neonatal intensive care units.

Crossover design with random ordering of condition. Following informed consent, an audio recording of the mother talking soothingly to her baby was filtered to simulate the mother's voice traveling through amniotic fluid. A final 10-minute recording of repetition of mothers' talking was recorded with maximum peaks of 70 decibels (dB) and played at levels ranging between 60 and 70 ambient decibels (dbA), selected above recommendations of the American Academy of Pediatrics in order to be heard over high ambient noise in the settings. This was played to her infant by a portable cassette tape player 3 times daily during a 48-hour period after feedings (gavage, bottle, or breast). At the end of 48 hours when blood work was required for clinical purposes, using a crossover design, the infant underwent the heel lancing with or without the recording being played. The order of condition was randomized, and the second condition was within 10 days. The Premature Infant Pain Profile (PIPP) was used as primary outcome. This is a composite measure using heart rate, oxygen saturation, 3 facial actions, behavioral state, and gestational age. This measure has demonstrated reliability and validity indexes.

There were no significant differences between groups on the PIPP or any of the individual components of the PIPP except a lower oxygen saturation level in the voice condition following the procedure. The second condition, regardless of whether it was voice or control, had higher heart rate scores and lower oxygen saturation scores even in the prelance baseline and warming phases. Order did not affect PIPP scores or facial actions.

Different modalities of maternal presence would appear to be necessary to blunt pain response in infants, and recorded maternal voice alone is not sufficient. The loudness of the recording may have obliterated the infant's ability to discern the mother's voice and may even have been aversive, reflected in decreased oxygen saturation levels in the voice condition. Preterm neonates of 32 to 36 weeks' gestation may become sensitized to painful experiences and show anticipatory physiological response.