This pilot trial will investigate whether it is possible to evaluate MiQuit in a multi-centre RCT located within the NHS, using research network resources. This study will recruit 400 pregnant smokers who will be randomly allocated to either MiQuit or control, and will provide estimates for the parameters required for determining the necessary resources for a definitive trial. These include: the range of recruitment rates in different centres; quit rates amongst participants; feasibility of assessing smoking status of trial participants in later pregnancy and ascertainment rates obtained; and the likely effect of MiQuit when women are offered this in NHS settings.