Midwives’ position in maternal and newborn care (MNC) in the Netherlands is unique: unlike many other countries, they have retained the authority over risk assessment and referral. We studied why and how midwives formally gained their position as gatekeepers, a role formally granted in 1987 by the Study Group for the Revision of the Kloosterman List (SGKL), a group of representatives from all professions and organisations involved in Dutch MNC. We analysed the minutes of the SGKL’s meetings and conducted interviews with eight key-informants who were involved in the SGKL’s decision process. We used theories of professional boundary work and cultural theories of risk to analyse the negotiations regarding the authority over risk assessment and referral in MNC that occurred between the representatives of midwives, general practitioners, and obstetricians in the SGKL. Our study offers new insights into professional boundary demarcation and the contest for control of risk management that occur at the political level of MNC. We show that beliefs regarding risks associated with childbirth and concern with the protection of professional interests can differ not only between but also within professions that seek to police and extend their boundaries. Negotiations are shaped by a dynamic interaction between these beliefs and interests, creating the possibility for otherwise unexpected transprofessional coalitions and redefining boundaries in unexpected ways. Our findings offer the possibility to view disputes in MNC as occurring between beliefs and interests, instead of between professional groups. These insights can reframe policy discussions in MNC and point to the need for further analysis of the boundary work that occurs in political and regulatory arenas.