The impact of preconception smoking and folic acid supplement use on maternal and child outcomes and disparities: a study protocol

Background Preconception interventions represent a pivotal yet often underutilised opportunity to improve maternal and child health. Substantial disparities in preconception health persist and important knowledge gaps remain, notably the impacts of optimising maternal preconception behaviours on a wide range of health, health service use, and childhood educational outcomes. Using linked, routinely-collected data, this study will quantify the impact of hypothetical preconception behavioural modification interventions on i) maternal and child outcomes, including health, health service use, and education, and ii) sociodemographic disparities in outcomes. Methods Data will be derived from the Education and Child Health Insights from Linked Data (ECHILD), a national resource combining health, education, and social care records. This study will include pregnancies recorded in England between April 2018 and March 2022. Preconception folic acid supplement use and smoking cessation will be examined in relation to a range of maternal, pregnancy, birth, and child outcomes (e.g., pre-eclampsia, preterm birth, delivery method, length of postnatal hospital stay, early Special Educational Needs and Disability provision). Analyses will estimate the effect sizes of hypothetical preconception behavioural modifications (e.g., halving preconception smoking prevalence or doubling preconception folic acid supplement use prevalence). Population attributable fractions will quantify the proportion of adverse outcomes that could be prevented through preconception behavioural modifications. The analyses will also explore disparities by maternal ethnic background and level of area deprivation. Directed Acyclic Graphs will be used to achieve parsimonious modelling of confounding variables (e.g., maternal age, parity) to produce adjusted population attributable fractions. Ethics and Dissemination Ethical approvals for analyses of the ECHILD database are detailed in this protocol. A multi-layered dissemination strategy will contribute to making the findings accessible and relevant to both academic and non-academic audiences. Extensive collaboration with public contributors has informed, and will continue to inform, this study and the dissemination of findings.