Through the analysis of three users' organisations, we demonstrate the importance of activities such as the collection, production and dissemination of knowledge in the functioning of these organisations: they are crucial in building users' representations, in creating a space for exchange and negociation with professionals and in setting up « matters of concern » and their publics. Thus, they contribute to install users' organisations as full participants to the childbirth politics. © 2012 Springer-Verlag France.