Unveiling developmental delays in early childhood: insights from a comparative study of the Bayley Scales (BSID-III) and the ASQ-3 in Iran.

Background: Developmental delay in early childhood is a significant concern with multifaceted causes and implications. The Bayley Scales of Infant and Toddler Development (BSID-III) is widely used for developmental assessment, but its use in Iranian children has been understudied. This study aimed to evaluate the developmental delays of Iranian children aged 1 to 42 months, investigate the association between parental education and these developmental outcomes, and compare developmental outcomes between the BSID-III and the Ages and Stages Questionnaire, Third Edition (ASQ-3).