Neurodevelopmental outcome of Italian preterm children at 1 year of corrected age by Bayley-III scales: an assessment using local norms

Background: Premature birth is often associated with neurodevelopmental difficulties throughout childhood. In the first three years of life, the Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III) constitute one of the most used tools for assessing child development. Since Bayley-III original norms are based on United States (US) population, it remains uncertain whether their use in other countries (e.g., European) is appropriate. Aims: This research aimed to examine neurodevelopment of preterm infants and full-term infants, using Bayley- III US norms in comparison to Italian (IT) norms. Patterns of developmental outcomes for both infant groups were also explored. Methods: 104 preterm and 58 full-term infants were included in the study. Bayley-III was used for neurodevelopmental assessment at 1 year of corrected age, considering both IT and US norms for scores computation. Results: Comparing scores obtained with IT vs US norms, differences in means were all significant across five subscales (p < 0.05 at least) for preterm infants, whereas for full-term peers significant differences were found only for Receptive Language and Fine Motor subscales (p < 0.001). Effect size (η2) ranged from 0.22 to 0.94. Within each group, significant discrepancies across subscales were found. Moreover, Italian preterm infants had significantly lower performances than full-term peers, excepting for Expressive Language and Gross Motor subscales. Conclusions: As regards to Italian 1-year children, our study seems to provide evidence for the tendency of Bayley-III US norms to overestimate development compared to IT norms. These findings emphasize the need to early detect children at risk for developmental delay and to plan early intervention.