Vocal development of infants with very low birth weight.

This study describes the vocal development of infants born with very low birth weights (VLBW). Samples of vocalizations were recorded from three groups of infants when they were 8, 12 and 18 months of age: preterm VLBW infants with bronchopulmonary dysplasia (BPD), preterm VLBW infants without BPD, and healthy full-term infants. Infants with BPD produced significantly smaller canonical syllable ratios than the full-term infants throughout the period of study. Premature VLBW infants who did not suffer from BPD produced relatively little canonical babble at 8 months of age, but were performing within the range of the full-term infants at 18 months of age. At 18 months of age, the infants with BPD were reported to have significantly smaller expressive vocabulary sizes than the healthier preterm and full-term infants.