In France, women can be incarcerated during pregnancy and can keep their babies with them in prison up to the age of 18 months. The small number of nurseries in France and their unequal geographic distribution as well as the high percentage of foreign prisoners often result in women's isolation from their usual cultural environment. Family members and cultural community play a crucial role in the process of mothering. The aim of this study is to explore through these mothers’ narratives how they experience the cultural aspects of this process in the prison environment. We conducted semi-structured interviews to collect the experience of 25 mothers and 5 pregnant women in 13 different prison nurseries in France and used interpretative phenomenological analysis to explore the data. Four different themes emerged: prison: repression of cultural practices, prison: a culture of its own, loss of traditional culture, and cultural hybridization. The specific environmental architecture and operating rules in prison nurseries may induce acute repression regarding cultural ways of mothering. Considering both cultural permeability specific to the peripartum period during which women tend to more easily embrace cultural aspects from their environment, and family distance which restrains cultural transmission, these mothers gather multiple factors of vulnerability for full prisonization, as a form of forced assimilation to prison culture. But a sort of specific hybrid prison culture around motherhood seems to emerge instead, in a process similar to creolization.