In the last decade a new form of participation of the citizens in research activities and in the production of knowledge has emerged.This development has started to reach epidemiological research, as illustrated in the recent section "EpiChange" of the journal Epidemiologia e Prevenzione. The conduction of epidemiological research through the engagement of citizens and new forms of production of knowledge - including peer-production - is still in its infancy. In 2005,we started in Italy a birth cohort, the NINFEA project, which uses the Internet to recruit pregnant women and to follow-up their children. Participants are volunteers who decide to take part in the research project. In this paper, we consider the aspects of the NINFEA project that are consistent with the concept of collaborative production of knowledge. In particular,we discuss issues related to the motivation of the participants, the selection of the research hypotheses to be evaluated and the definition of the population of interest of the study.