The meaning of human rights for children is a contested issue; the notion of rights for unborn babies poses additional complexity. Drawing on data from a prospective case study of a specialist drug and alcohol obstetric provider and the statutory child protection service, this article discusses family engagement within a child-rights framework, and demonstrates how adherence to the "best interests" principle, in the absence of an appropriate service provision, excludes vulnerable mother/infant dyads from drawing on extended family support.