Prevalence of developmental disabilities appears to have increased over time, and children of immigrant backgrounds maybe particularly at risk. Using population-based data linkage and register-based studies this was explored in Australian- born children from 1980 to 2017 according to maternal country of birth. Adverse pregnancy, birth and neonatal outcomes, increased prevalence of autism spectrum disorder with intellectual disability and cerebral palsy with intellectual disability, higher hospitalisation rates of children with developmental disabilities and greater severity of autism spectrum disorder with intellectual disability were all Identified, in children of foreign-born mothers from low- and middle-income countries. Maternal migration may be influencing developmental disabilities and disease severity. Improvements to developmental surveillance and culturally appropriate assessment tools may help better identify developmental outcomes in Western Australian children of immigrant mothers.