Traditionally, Euroamerican cultures have considered that human status was conferred at the conclusion to childbirth. However, in contemporary Euroamerican biomedicine, law and politics, the living subject is often claimed to pre-exist birth. In this book Lorna Weir argues that the displacement of birth as the threshold of the living subject began in the 1950s with the novel concept of perinatal mortality referring to death of either the foetus or the newborn just prior to, during and after birth.

Weir traces the introduction of the perinatal threshold into child welfare and tort law through expert testimony on foetal risk, sketching the clash at law between the birth and perinatal thresholds of the living subject. Her book makes original empirical and theoretical contributions to the history of the present (Foucauldian research), feminism, and social studies of risk, and she conceptualizes a new historical focus for the history of the present: the threshold of the living subject - the historically and culturally variable processes through which the boundary of human status is established at the points of entry and exit into collective existence.

This book calls attention to the significance of population politics, especially the reduction of infant mortality, for the unsettling of the birth threshold. Weir argues that risk techniques are heterogeneous, contested with expertise, and plural in their political effects rather than singular, neoliberal, and uniformly supported by expertise.