The MOHMQuit (Midwives and Obstetricians Helping Mothers to Quit Smoking) Trial: protocol for a stepped-wedge implementation trial to improve best practice smoking cessation support in public antenatal care services

BACKGROUND: Smoking during pregnancy is the most important preventable cause of adverse pregnancy outcomes, yet smoking cessation support (SCS) is inconsistently provided. The MOMHQUIT intervention was developed to address this evidence-practice gap, using the Behaviour Change Wheel method by mapping barriers to intervention strategies. MOHMQuit includes systems, leadership and clinician elements. This implementation trial will determine the effectiveness and cost-effectiveness of MOHMQuit in improving smoking cessation rates in pregnant women in public maternity care services in Australia; test the mechanisms of action of the intervention strategies; and examine implementation outcomes. METHODS: A stepped-wedge cluster-randomised design will be used. Implementation of MOHMQuit will include reinforcing leadership investment in SCS as a clinical priority, strengthening maternity care clinicians’ knowledge, skills, confidence and attitudes towards the provision of SCS, and clinicians’ documentation of guideline-recommended SCS provided during antenatal care. Approximately, 4000 women who report smoking during pregnancy will be recruited across nine sites. The intervention and its implementation will be evaluated using a mixed methods approach. The primary outcome will be 7-day point prevalence abstinence at the end of pregnancy, among pregnant smokers, verified by salivary cotinine testing. Continuous data collection from electronic medical records and telephone interviews with postpartum women will occur throughout 32 months of the trial to assess changes in cessation rates reported by women, and SCS documented by clinicians and reported by women. Data collection to assess changes in clinicians’ knowledge, skills, confidence and attitudes will occur prior to and immediately after the intervention at each site, and again 6 months later. Questionnaires at 3 months following the intervention, and semi-structured interviews at 6 months with maternity service leaders will explore leaders’ perceptions of acceptability, adoption, appropriateness, feasibility, adaptations and fidelity of delivery of the MOHMQuit intervention. Structural equation modelling will examine causal linkages between the strategies, mediators and outcomes. Cost-effectiveness analyses will also be undertaken. DISCUSSION: This study will provide evidence of the effectiveness of a multi-level implementation intervention to support policy decisions; and evidence regarding mechanisms of action of the intervention strategies (how the strategies effected outcomes) to support further theoretical developments in implementation science. TRIAL REGISTRATION: ACTRN12622000167763, registered February 2nd 2022. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13012-022-01250-3.