Mother and child wellbeing are intimately connected during pregnancy and the first 12 months of the infant's life. The fetus and child directly experience the mother's life and are shaped by it. A mother's environmental experiences, physical health, and psychological distress affect her interactions with her infant, which in turn have physiological, neurological, and psychological consequences that extend far into the future. In this article, Alexandra O'Sullivan and Catherine Monk explore the biological and behavioral pathways through which the physical and psychological toll of environmental experiences such as poverty, trauma, pollution, lack of access to good nutrition, and systemic disadvantage is transmitted from mother to child, thus impairing fetal and infant neurobiological and emotional development. Fortunately, there are ways to buffer these risks and reorient both the child and the mother-child pair toward a strong developmental trajectory. The authors examine promising avenues for policy makers to pursue. Chief among these are policies that increase access to health care, including mental health care, and those that reduce family stress during pregnancy and the postpartum period, for example, by boosting family income or allowing parents to take paid leave to care for their newborn children.