Effectiveness of the BabyBreathe intervention for maintaining postpartum smoking cessation: multicentre pragmatic randomised controlled trial.

OBJECTIVE: To assess the effectiveness of an interpersonal and digital intervention, BabyBreathe, for maintaining postpartum smoking cessation. DESIGN: Multicentre pragmatic individually randomised controlled trial. SETTING: Community health visiting services in the UK. PARTICIPANTS: 887 pregnant women and people who reported quitting smoking in the 12 months before, or during, pregnancy, with abstinence verified by exhaled carbon monoxide readings. A secure web based randomisation sequence, stratified by recruitment hub, partner smoking status, and quit timing (before or during pregnancy), was used to randomise participants (1:1) to receive the intervention or usual care. The trial was unblinded. INTERVENTION: BabyBreathe comprised in-person or remote smoking cessation maintenance interpersonal support at 28-32 weeks' gestation and 10-14 days post partum. The BabyBreathe box, posted at the time of birth notification, contained theory driven advice for cessation maintenance, a sample of nicotine replacement gum, and motivational tools. Tailored motivational and educational text messages were provided. A website and app provided tailored cessation maintenance advice, social support, motivational tools, and gamification. Control was usual postpartum care. MAIN OUTCOME MEASURE: The primary outcome was continuous smoking abstinence, verified by exhaled carbon monoxide concentration (≤7 parts per million (ppm)) 12 months post partum. RESULTS: Between 4 September 2021 and 3 August 2023, 887 participants were randomised: 442 to receive BabyBreathe and 445 to receive usual care. After one post-randomisation exclusion, 886 participants were included in an intention-to-treat analysis. The group difference in smoking abstinence at 12 months post partum was not significant (BabyBreathe 242/441 (54.9%) v usual care 222/445 (49.9%); odds ratio 1.23, 95% confidence interval (CI) 0.94 to 1.60, P=0.13, risk difference 4.8% (-1.7% to 11.2%), and number needed to treat (NNT) 21 (NNT to benefit 8.9 to ∞) and NNT to harm 59). A post hoc per protocol analysis favoured the intervention (BabyBreathe 200/347 (57.6%) v usual care 222/445 (49.9%); adjusted odds ratio 1.36, 95% CI 1.02 to 1.81, P=0.04), risk difference 7.2% (0.3% to 14.1%), and NNT 13.9 (7.1 to 333.3). No trial related adverse incidents occurred. CONCLUSIONS: BabyBreathe did not statistically significantly increase sustained smoking abstinence post partum for people who quit smoking in pregnancy. A post hoc per protocol analysis, including only those who received interpersonal support as intended, showed statistically significantly greater benefit from BabyBreathe over usual care. A focus on fidelity and further targeting of BabyBreathe to groups with lower socioeconomic status may be warranted. TRIAL REGISTRATION: ISRCTN Registry ISRCTN70307341.