BackgroundThis study addresses children of parents with intellectual disability in Norway. The aim was to examine: (i) the impact of definitions of intellectual disability on prevalence, (ii) whether numbers were increasing, (iii) the prevalence of motherhood and fatherhood and (iv) rates of lost custody. MethodsAnalyses of national registers (n=30834) and mapping in four municipalities (n=85). Results0.19% of all children had parents with recorded intellectual disability, increasing to 0.87% with wider inclusion criteria. The number of children born to parents with intellectual disability has been declining since the mid-1980s. The proportion of mothers with intellectual disability was twice that of fathers. Parental custody was revoked for 30-50% of children, with single mothers being at particular risk. Parents with intellectual disability accounted for 20-25% of all custody cases. ConclusionsThe results show that prevalence depends on the definition of intellectual disability. The decreasing number of children and the need for development of specially adapted family supports are discussed.