Effect of financial voucher incentives provided with UK stop smoking services on the cessation of smoking in pregnant women (CPIT III) : pragmatic, multicentre, single blinded, phase 3, randomised controlled trial

Objective: To examine effectiveness, cost-effectiveness, generalizability and acceptability of financial incentives for smoking cessation during pregnancy ‘bolted-on’ to variously organised UK SSSs. This paper reports effectiveness. Design: A prospective pragmatic, multi-centre, parallel group, single-blinded, individually randomised controlled superiority trial with 1:1 allocation augmented by embedded cost-benefit and mixed methods studies of generalisability and acceptability. Setting: Seven UK SSSs provided in primary and secondary care facilities in Scotland, Northern Ireland and England. Participants: 944 pregnant self-reported smokers (at least 1 cigarette in the last week) when asked at first maternity visit, ≥16 years, <24 weeks gestation notified to the trial team by routine SSSs entered the study. 941 (471 intervention, 470 control) completed the study as 3 asked for their data to be removed. Interventions: The offer of usual SSS support for control participants with the addition of up to £400 ($523, 583 euros) of LoveToShop financial voucher incentives for engaging with current SSSs and/or quitting smoking during pregnancy ‘bolted-on’ with intervention (bolted-on - current services changed as little as possible). Outcomes: The primary outcome was self-reported smoking cessation in late pregnancy (random date between 34-38 weeks gestation) corroborated by saliva cotinine (and anabasine if using nicotine replacement products). Secondary outcomes included point and continuous abstinence 6 months after expected date of delivery, engagement with SSS, biochemically validated abstinence 4 weeks later, birth weight, cost-effectiveness, generalisability documenting SSS formats and acceptability to pregnant women and their carers. Results: 126/471(26.8%) quit from the intervention group and 58/470(12.3%) from the control group AOR 2.78 (1.94 to 3.97) p<0.001 - adjusted for age, smoking years, Index of Multiple Deprivation, Fagerström score, pre or post COVID, recruitment site. Serious Adverse Events (SAEs) were early miscarriages and other ‘expected’ pregnancy events requiring hospital admission and all SAEs were unrelated to the intervention. Most who quit from both groups relapsed after their baby was born. Conclusions: The offer of up to £400 of financial voucher incentives to stop smoking during pregnancy ‘bolted-on’ to current heterogeneous UK Stop Smoking Services is highly effective. This bolt-on intervention will help implement new NICE guidance which includes the addition of financial incentives to support pregnant women to stop smoking. Continuing incentives to 12 months after birth are being examined to prevent relapse.