This paper explores how the theory of the Malthusianism of poverty applies in the context of the slums of Mumbai. In fact, despite a declining fertility level, Indian women continue to give birth at young age and with short inter-birth intervals. The Malthusianism of poverty explains this paradox. In this paper, we will highlight three nuances that could be brought to this model. First, extreme poverty can constitute an obstacle to the use of birth control methods, since a minimal degree of agency seems to be required to resort to family planning. Second, gender discrimination in the sex of children (the well-known “son preference”) and religion have a huge impact on couples’ choice of contraception. Third, women empowerment plays an important role in the decision about family planning. We conclude on the integration of two apparently antagonist theories: following a logic of immediate survival (the model of the Malthusianism of poverty), couples tend to practice birth control, which mostly means sterilization. However, thanks to better educational levels, children – less numerous and better educated – will be able to help their parents in their old age (Caldwell’s theory of fertility decline).