Background: The capacity for midwifery to improve maternity care is under-utilised. Midwives have expressed limits on their autonomy to provide quality care in relation to intrapartum fetal heart rate monitoring. Aim: To explore how the work of midwives and obstetricians was textually structured by policy documents related to intrapartum fetal heart rate monitoring. Methods: Institutional Ethnography, a critical qualitative approach was used. Data were collected in an Australian hospital with a central fetal monitoring system. Midwives (n = 34) and obstetricians (n = 16) with experience working with the central fetal monitoring system were interviewed and observed. Policy documents were collected and analysed. Findings: Midwives’ work was strongly structured by policy documents that required escalation of care for any CTG abnormality. Prior to being able to escalate care, midwives were often interrupted by other clinicians uninvited entry into the room in response to the CTG seen at the central monitoring station. While the same collection of documents guided the work of both obstetricians and midwives, they generated the expectation that midwives must perform certain tasks while obstetricians may perform others. Midwifery work was textually invisible. Discussion and conclusion: Our findings provide a concrete example of the way policy documents both reflect and generate power imbalances in maternity care. Obstetric ways of knowing and doing are reinforced within these documents and continue to diminish the visibility and autonomy of midwifery. Midwifery organisations are well placed to co-lead policy development and reform in collaboration with maternity consumer and obstetric organisations.