Actively involving people in self-monitoring and management during their pregnancy is an emerging clinical and social practice. Self-monitoring of blood pressure and self-testing for proteinuria, key diagnostic tests for pre-eclampsia, are becoming commonplace in hypertensive pregnancies. While evidence exists on the acceptability and feasibility of self-monitoring blood pressure, evidence for self-testing for proteinuria in pregnancy is thin, with little knowledge of how it might affect the traditional structures of maternity care. As part of a diagnostic accuracy study on self-testing for proteinuria, pregnant people and healthcare professionals were recruited to a qualitative study to understand their experiences of, and attitudes to, self-testing. Multiple qualitative methods were used, including interviews, focus groups, and free text postcards. A discourse analysis was conducted to understand how self-testing might inform and reshape routine antenatal care. Analysis revealed a tension between the empowering concept of participatory surveillance, which pregnant people and healthcare professionals were broadly positive about, and the adjudications made by healthcare professionals about the candidacy, or suitability, of certain pregnant people to self-test. Candidacy is a framework for understanding what influences access to healthcare for socially disadvantaged groups, including professional judgments that impact access to interventions. While participatory surveillance was felt to have the potential to empower pregnant people in antenatal care, the loss of the traditional clinical gaze was disquieting for some, and pregnant people and healthcare professionals were reluctant to cede professional responsibility.