Children without identified developmental delays, genetic conditions, or major perinatal complications, assessed as part of the general population.

Children with identified developmental delay based on prior clinical assessment or referral information, without a confirmed specific genetic diagnosis.

Children with confirmed genetic conditions associated with developmental risk, based on medical documentation provided by parents or caregivers.

Children born preterm between 33 and 37 weeks of gestational age. This group includes infants and toddlers with a history of moderate to late prematurity, without severe neonatal complications requiring classification as extremely preterm.

Children born before 33 weeks of gestational age. This group includes infants and toddlers with a history of extreme prematurity, associated with increased risk for developmental difficulties across multiple domains.

All participants undergo a standardized psychological developmental assessment conducted by trained specialists. The assessment includes structured diagnostic tasks and direct observation of the child's behavior during play and natural interaction, carried out in the presence of a parent or legal guardian. In addition, parents or caregivers complete standardized questionnaires assessing the child's social-emotional functioning and adaptive behavior. No experimental intervention or therapeutic procedure is applied.

Cognitive functioning assessed using the Cognitive Scale of the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4). The scale evaluates early cognitive abilities, including sensory-motor processing, exploration and manipulation, object relations, memory, problem solving, and early executive functioning. Data will be reported as a Composite Score ranging from 40 to 160, where higher scores indicate better cognitive development.

Language functioning assessed using the Language Scale of the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4), including receptive and expressive communication abilities appropriate to the child's developmental level. Data will be reported as a Composite Score ranging from 40 to 160, where higher scores indicate better language development.

Motor functioning assessed using the Motor Scale of the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4), including fine and gross motor skills related to coordination, posture, locomotion, and motor planning. Data will be reported as a Composite Score ranging from 40 to 160, where higher scores indicate better motor development.

Social-emotional development assessed using the Social-Emotional Scale of the Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4), based on parent-reported information regarding emotional regulation, social engagement, communication of needs, and relationship development. Data will be reported as a Scaled Score ranging from 1 to 19, where higher scores indicate better performance.

Author-designed socio-demographic questionnaire completed by parents or caregivers, including information on the child's sex, month and year of birth, gestational age at birth, place and region of residence, parental education level and selected perinatal characteristics.