Nicotine replacement therapy (NRT) helps pregnant women quit smoking. Usual National Health Service (NHS) cessation care in pregnancy starts only after women stop smoking and comprises behavioural support and NRT. NRT is stopped if women restart smoking. We hypothesised that NRT would have a bigger effect on cessation in pregnancy if used: (1) to reduce smoking before quitting (‘preloading’), (2) during brief smoking lapses after quitting and (3) to help those who cannot stop smoking, to reduce instead.

A two-arm parallel group, open-label, multicentre, assessor-blind randomised controlled trial. Participants are recruited at hospital antenatal clinics and other NHS settings throughout England and Wales or via social media advertising. Those enrolled are in antenatal care,

Ethics approval was granted by the West Midlands—Coventry & Warwickshire Research Ethics Committee (REC reference: 21/WM/0172; Protocol number 21001; IRAS Project ID: 291236). Written informed consent will be obtained from all participants. Findings will be disseminated to the public, funders, relevant practice and policy representatives and other researchers.

ISRCTN84798566.