The article analyzes the legal and medical significance of the child's living together with his mother in the Children's Houses of the penitentiary system. Materials for the study were the author's own observations, the materials of the Federal Service for Execution of Punishment (FSEP) of Russia reports on medical care for women and children over the period of five years; the data obtained as a result of targeted inquiries to the Children's Houses of the penitentiary system. The article generalizes the experience of the Children's House activities of the penitentiary system in this direction. It shows the positive effect of joint maintenance, first of all, in terms of the breastfeeding rates. Natural and mixed feeding constituted 67 % in the Children's Houses, including 85 % in the Children's Houses with joint stay of the newborns, and 42 % in other Children's Houses, which is statistically lower. In the Children's Houses with the expanded co-residence department, the primary morbidity of children was 1678 ‰, while in the comparison group - 2015 ‰, which is significantly higher. According to the primary incidence rate, there was a decrease in the pool of respiratory diseases from 1000 to 870 per 1000 children, thanks to placing into operation of the joint co-residence hostel for mother and child. The co-residence of the mother, convicted to imprisonment, and the newborn will contribute to the childs physical, neuropsychic development, its harmonious growth, as well as to manifesting the maternity feelings, which can be an important factor of the resocialization of the convicted person. The author propose to introduce a normative compulsory co-residence of mother and child in the Children's Houses of the penitentiary system.