The aim of this thesis was to increase the knowledge about children born to mothers with an intellectual or developmental disability by investigating incidence (Study I), support at the stra tegic level (Study II), support at the family level (Study III), and experiences of having grown up with a mother with a developmental disability (Study IV). The first study investigated the 5-year incidence of children being born to mothers with an intellectua l disability in a Swedish county. Three types of registers were used, together with personal identification numbers. The resulting incidence rate, 2.12 children per 1,000 children indicates that there are currently approximately 4000 children (aged 0-18 years) that have been born to a mother with an intellectual disability in Sweden. Data for Studies II and III were collect ed by means of focus group interviews with 29 professionals supporting families with parental intellectual disability, and the data were analysed by means of content analysis. Study II described results on the strategic level of support; roles and activities of the professionals involved, identification of families in need, problems with identifying mothers with an intellectual disability, existing collaboration and dilemmas concerning legislative actions. The results indicated a rich web of support to these families from all kinds of welfare sectors, but further needs for building collaboration were identified, such as the need to coordinate education efforts. Study III described results on the family level of support: support practices, pedagogical strategies, and maintaining the child perspective. The results indicated the need for concrete training, the importance of involving the father/ partner, and the value of not losing the child perspective and of creating support practices with a clearer focus on the children. In Study IV, four women were interviewed about their experiences of growing up in a family with a mother who has a developmental disability. Narrative inquiry and content analysis were employed. The findings showed recollections of a vulnerable childhood filled with worries, fear, and anxiety, and with a strong feeling of responsibility. No effective support from the authorities was ever offered to the four informants, who dealt differently with their lives as adults with regard to their own family and children. The results of this thesis provide new knowledge about the complex situation of being a child in a family with maternal intellectual or developmental disability, and they may be used by staff in the welfare sectors in order to improve the visibility of these children and offer support adapted to the children's situation.