This Special Issue elucidates how Mexican obstetricians, mothers, feminists, scientists, and politicians understood the intersections of reproduction and birth control with the politics of national identity and modernization over the course of a century. Each article investigates these changes within a global context, given that Mexican women and men working in and advocating for reproductive health participated in transnational networks that mobilized concerns about pronatalism, eugenics, sexuality, and population control. Several authors examine how foreign mediators and international foundations rooted in the United States and Europe became involved in Mexico’s politics of reproduction. Collectively, these works underscore how views of reproduction intertwine with nationalist projects and patriarchal systems. These works interrogate the continued legacies of colonialism and eugenics on the contours of public debates about family planning in Mexico. Despite these public debates, Mexican women worked to exercise control over their reproductive capacities by gaining access to abortions, contraceptives, and securing the material conditions necessary to raise the number of children they desired.