Neurobehavioral functioning of healthy preterm infants of varying gestational ages.

Little information is available regarding the behavioral repertoire of healthy, yet prematurely born, infants. To address this problem, the Assessment of Preterm Infants' Behavior (APIB) was used 10 to 14 days after birth in a cross-sectional comparison of 42 healthy newborn infants: 16 full-term infants (gestational age at birth [GA] = 40 weeks), 13 close to full-term infants (GA = 37 weeks), and 13 preterm infants (GA = 34 weeks). Groups differed on four background variables that were used as covariates in subsequent analyses. Significant group differences were found on 12 of 29 outcome variables, including measures of autonomic, motor, state, attention/interaction, and self-regulatory systems, as well as a measure of overall behavioral organization. Pairwise comparison showed that preterm and full-term infants differed on all 12 variables whereas preterm and close to full-term infants differed on 11 of the 12 variables. Furthermore, full-term and close to full-term infants differed on 4 of the 12 variables, including measures of the autonomic, motor, and state systems. Full-term and close to full-term infants were behaviorally more similar to one another than either group was to the preterm infants, yet there were important differences even between full-term and close to full-term infants.