Premature baby cries remain different from those of full-term babies

Prematurity is known to increase the risk of organic or functional pathologies from the neonatal period as well as after birth. The impact of prematurity on the acoustic structure of cries, which are vital signals for survival of babies, has received little scrutiny, despite its prognostic potential. Here, we test the hypothesis that the acoustic structure of the cries of preterm babies changes with their growth, ultimately becoming identical to the cries of full-term infants. We recorded and analyzed the cries of 18 premature babies, born between gestational age 26 and 33 weeks, every week while they were hospitalized in a neonatal intensive care unit. Our results show that as premature babies approach their theoretical term, their cries become increasingly tonal, less marked by noisy components, and carrying individual cues. We then compared these cries with those recorded in 25 healthy full-term babies. Despite the evolution of premature baby cries over time, the acoustic structure of these cries remains different from that of full-term infants. These results suggest that the vocal maturity of premature babies is not fully attained at the theoretical age of term.