Families presenting to the developmental clinic have more socio-economic disadvantage compared with the referring district. This has implications for service delivery and clinical presentation, and highlights the importance of the social worker's role in a developmental diagnostic team.

Socio-economic advantage and disadvantage are associated with stable scores, but introducing intervention is associated with improved scores. Deterioration is most likely in children with chromosomal variations or neuro-motor disabilities, and regular reassessment of these children is recommended.

Children with GDD without autism were more likely to be disadvantaged and to have had contact with child protection services than children with ASD. This has implications for the assessment, early intervention and support services for children with disabilities and their families.