While pain in childbirth is a universal, cross-cultural, biological reality, individual experiences and perceptions of this pain are historically and culturally specific. At the turn of the 20th century-a key period in terms of both the medicalisation of birth and the professionalisation of obstetrics in the Canadian context-Canadian physicians understood and conceptualised 'birth pangs' in a number of varying (and at times competing) ways. Throughout the 19th century, doctors emphasised the broader utility of pain as a diagnostic tool and a physiologically necessary part of the birthing process. With the advent of anaesthetics, including chloroform and ether, however, a growing subset of the medical profession simultaneously lauded the professional, physiological, and humanitarian benefits of pain relief. By the first decades of the 20th century, shifting understandings of labour pain-and particularly growing distinctions between 'pain' and 'contraction' in mainstream medical discourses-underscored the increasing use of obstetric anaesthesia. Drawing on a broad range of medical texts and professional literature, and focusing on a key historical moment when the introduction and adoption of a new medical technology opened up possibilities for professional debate, this paper unpacks both the micropolitics and the macropolitics of shifting understandings of labour pain in modern Canadian medical history.