BACKGROUND: Equal access for all based on need is part of a conceptualisation of quality underpinning recent UK NHS policies. OBJECTIVE: To develop metrics for access to maternity care from routinely available data in order to inform inequalities monitoring and commissioning. DESIGN: Cross-sectional cohort design using case-note audit and postnatal questionnaire. SETTING: London hospital, UK, in an area of relative socio-economic deprivation. METHODS: Stage 1: Identification of potential markers. Stage 2: Testing of markers via case note audit and postnatal questionnaire. Stage 3: Selection of final basket of markers of access to maternity services. RESULTS: Of 71 possible markers identified, 32 used information obtainable from maternity case notes. After testing in the case-note audit, 21 were discarded, and 11 included in the final basket covering: timely entry to maternity care; appropriate assessment and identification of needs of individuals; referral and communication with other related health and social care services. CONCLUSION: It is possible to devise a local basket of markers covering a range of important entry and in-system access metrics. Such a tool offers an unobtrusive means to audit the effectiveness of some of the processes intended to help women move through the maternity and related health and social care systems during pregnancy, and to monitor progress on reducing social inequalities in access over time.