Neonatology is a recently specialized area of medicine in which medical advances continue to save the lives of many ailing infants. However, like most areas of health care, it is not a perfect science, and hence not all infants can be saved, no matter how advanced the technology or how well-trained the physician. Inevitably, decisions regarding when to forego treatment must be made. It is essential to scrutinize the bases upon which these decisions are reached. This article examines the development of the scientific, legal and philosophical theories in Canada, the United States and the United Kingdom in an attempt to delineate a nexus wherein these theories link together to found medical decisions in the neonatal intensive care unit. Legal rules of medical decision making are informed by standards set by the medical profession as well as by principles of moral philosophy. However, in the face of medical uncertainty regarding outcomes, the content of the 'best interests' of the child standard increasingly relies upon a normative conception of the 'sanctity of life'. Ironically, as science pushes at the bounds of the meaning of 'medical futility', the sanctity of life position gains strength and is relied upon more frequently by the judiciary. The author concludes that both subjective and objective factors must inform this decision making in order to protect the best interests of the child optimally.