In this article, we describe and qualitatively analyze the only prison in the state of São Paulo that houses mothers and babies. By law, Brazilian women inmates are only able to personally care for their babies until they are 6 months old. After such period, babies are placed with relatives or institutionalized. In this study, systematic observations and interviews were conducted with 8 prisoners over a period of 6 months. Results show that the child developmental process inside the prison can be aggravated by two main conditions: there was no possibility for the caretaker and the child to be involved in a series of important activities for child stimulation and the physical condition of the building was inappropriate, causing respiratory diseases in the children and subpar sleeping conditions for mothers and babies.