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.