To explore facilitators and barriers to the implementation of a physiological approach to care during labour and birth in obstetric settings. To explore how facilitators and barriers located at three levels: organisation, professional groups (midwives and obstetricians) and women, interact to influence the implementation of a physiological approach. A systematic review of the literature, identified 32 eligible studies from four databases reporting relevant qualitative data. Findings from these studies were thematically synthesised in three phases: line by line coding of findings from primary studies, development of descriptive themes and analytical themes. This review is reported in line with PRISMA guidelines. At an organisational level, centralisation of care in obstetric units limited time for labouring and professional care to support a physiological labour and birth. Risk management strategies ostensibly designed to promote safety sustained a risk-based approach. At a professional level, important barriers include hierarchical decision-making led by obstetricians, midwifery acquiescence, obstetric and midwifery risk preoccupation, rationalisation of the routine use of clinical intervention and an erosion of midwifery skills and knowledge. At the level of the woman, barriers include a lack of knowledge and reliance on professional decision-making. Facilitators include collaborative working by midwives and obstetricians, a valuing of midwifery autonomy and women's questioning of inappropriate intervention use. Contrary to evidence-based guidelines that recommend a physiological approach, a risk-based approach informs practices in obstetric units. Primary research has mainly identified barriers to implementing a physiological approach at a professional level, and this has been studied largely from a midwifery perspective. To aid comprehensive investigations of facilitators and barriers and their interactive influences, this review identifies important research gaps for study across all levels: organisation, professionals (midwives and obstetricians) and women. Risk preoccupations and rationalisation, with negative influences on knowledge and skills in the use of a physiological approach, must prompt reflection and action amongst professional groups. Power imbalances between midwives and obstetricians need to be addressed, drawing on experiences in units where collaborative working and midwifery autonomy is fostered. Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.