BACKGROUND:
Improving maternity care remains a long-standing political and NHS priority. Responding to concerns raised about safety and quality, the 2016 Better Births review aimed to reform maternity care in England. Central to its recommendations was the Midwifery Continuity of Carer (MCoC) model, already deployed in some NHS services, but not yet widely adopted. Guidance issued following Better Births aimed to establish MCoC as the ‘national default model of care’.

OBJECTIVES:
Despite policy commitments, MCoC implementation progress varied, with concerns being raised by professional bodies, within commissioned reviews, and by the midwifery workforce. The SIMCA study (Study of Implementation of Midwifery Continuity of Carer) was designed to investigate the local, regional, and national factors shaping MCoC implementation across England.

METHODS:
We conducted 65 staff interviews and 32 service-user interviews across six geographically varied NHS Trusts in England. We observed meetings and collected key documents including implementation plans, Trust policies, and public reports. Our analysis was guided by two theoretical frameworks: the Consolidated Framework for Implementation Research (CFIR) and Normalisation Process Theory (NPT). Full NHS ethical approval was obtained.

RESULTS:
We show how local, regional, and national factors shaped the implementation of MCoC. Though sites demonstrated varied implementation pathways, none achieved full, sustained implementation, and all experienced delays, interruptions, or restarts. Key characteristics of the MCoC model – including the emphasis on intrapartum care and mandated team structures – proved particularly challenging. Despite facing such difficulties, maternity services demonstrated adaptability, and resilience.

CONCLUSIONS:
SIMCA highlights challenges involved in implementing wide-scale healthcare policy change (here, MCoC), where key structural and contextual factors limit sustained implementation.

KEY MESSAGE:
Implementation success requires an understanding of context and well-supported local systems. The Better Births MCoC model did not align with local, regional and national maternity contexts. Whilst widespread, at-scale implementation of MCoC was not achieved, innovative forms of continuity persist. Maternal mortality