Prenatal diagnosis (PND) was introduced in France in the 1970s on the initiative of medical researchers and clinicians. For many years the regulation of practices was self-imposed, decentralised and idiosyncratic. The advent of ‘therapeutic modernity’ in the 1990s gave rise to an ethical, legal and scientific framework designed to homogenise PND at a national level, with the creation of multidisciplinary centres (CPDPN) and the Agence de la biomédecine. This article first recovers the history of PND in France. It then compares the activities of two CPDPNs, using ethnographic fieldwork and by analysing national quantitative data compiled by the Agence. It argues that the official policy of nationally homogeneous practices is not born out in practice, at the local level. This lack of homogeneity is most apparent in the number of authorisations for pregnancy termination due to foetal malformation, which varies considerably from one centre to another. Rooted in local culture, this variation relates to organisational methods, decision-making processes and variable levels of tolerance towards the risk of disability. Foetal medicine practitioners, thus, maintain a certain amount of autonomy that is collective rather than individual and that is reflected in the particular ‘identity’ of a given centre.