Background Standardised developmental tests are now widely used in neurodevelopmental assessments of infants and children. In 2006, the revised and updated version of the Bayley Scales of Infant and Toddler Development (version III) replaced the previous version and is now widely used in neonatal developmental follow-up clinics. Several papers from Australia have highlighted underestimation of developmental impairment up to age 2 using this revised version. We aimed to ascertain how a cohort of healthy 3-year-old children performed compared to the standardised norms of the Bayley Scales of Infant and Toddler Development (version-III).

Method Term healthy newborn control infants from the prospective Development after Infant Surgery (DAISy) study were included. At 3 years of age, the mean scores on each of the five subscales for 156 children were compared with the standardised norms.

Results At 3 years of age, the mean scores were higher than the standardised norms on four of the subscales, cognition (<0.05), receptive and expressive language and fine motor (p<0.001). There was no significant difference in the gross motor scale (p=0.435).

Conclusions Healthy term Australian children have a statistically significantly higher mean score on the Bayley Scales of Infant and Toddler Development (version-III) compared with the standardised means in four of the subtests, with the greatest difference in receptive language. This has implications for the assessment of children as the test may miss those with a minor delay and not reflect the severity of delay of infants that it does identify. We recommend that consideration ought to be given to re-standardising this assessment on Australian children.