This article presents the results of an ethnographic observational study carried out in a maternity service from the point of view of a sociology of paternity. The author first shows how the maternity hospital is a « matricentered » institution. He then proposes a typology of the fathers’ behaviours in such a context. Lastly, he explains that the presence of fathers in maternity hospitals is important in that they learn there their legitimate parental competence that matrifocality tends to bias or to minimize.