Factors associated with postpartum return to smoking in two UK cohorts
Helping women quit smoking in pregnancy and remain abstinent postpartum is an important public health target. Approximately half of UK women who smoke will attempt to quit in pregnancy but, despite wishing to remain abstinent, up to 76% return to smoking within two years. Since the introduction of e-cigarettes, the methods people use to attempt to stop smoking have changed substantially. To investigate factors which influence postpartum return to smoking (PPRS) and whether these have changed since e-cigarettes became popular, we present findings from analyses of two longitudinal pregnancy cohorts conducted in 2011-2012, when e-cigarettes were not widely used, and in 2017, when they were, comparing the prevalence of and factors associated with PPRS.
The 2011-2012 cohort ‘PLS Nottingham’ recruited participants from antenatal clinics in two Nottingham hospitals. The 2017 cohort ‘PLS National’ was multicentre, recruiting from 17 hospitals in England and Scotland. In both cohorts, questionnaires were completed by pregnant women at baseline (8-26 weeks gestation), in late pregnancy (34-36 weeks) and at 12 weeks postpartum. These asked about women’s characteristics, smoking behaviours and, in PLS National, e-cigarette use. For each cohort, we calculated the prevalence of postpartum relapse in a subgroup of women that were abstinent in late pregnancy. In both subgroups, we conducted exploratory, multiple logistic regressions to identify factors significantly associated with PPRS.
From 850 women in the PLS Nottingham cohort, we identified a subgroup of 255 who reported having quit smoking at the late pregnancy questionnaire. In PLS National from 750 women we identified 162 women who had quit. Baseline characteristics for the groups were similar. The postpartum questionnaire response rate for women who had quit in late pregnancy in PLS Nottingham was 81.6% (n=208) and in PLS National 84.6% (n=137). Prevalence of PPRS was 25.2% (95% CI 0.20-0.32) in PLS Nottingham and 35.8% (95% CI 0.28-0.44) in PLS National. Factors independently and significantly associated with a change in relapse rates in PLS Nottingham were education at GCSE level or above (adjusted OR 0.25, 95% CI 0.07-0.91), breastfeeding at 12 weeks postpartum (adjusted OR 0.39, 95% CI 0.17-0.89) and reporting, in the postpartum, living with someone who smoked (adjusted OR 3.27, 95% CI 1.07-9.98). In PLS National, both breastfeeding at 12 weeks postpartum (adjusted OR 0.12, 95% CI 0.04-0.35) and having used an e-cigarette in pregnancy (adjusted OR 0.41, 95% CI 0.17-0.99) were associated with reduced PPRS rates.
Both before and after e-cigarettes became widely available, breastfeeding at 12 weeks postpartum was associated with lower PPRS rates. In the survey that measured it, e-cigarette use during pregnancy was also associated with a lower rate. Further qualitative work is required to understand why these associations are noted, and help design future interventions aimed at relapse prevention.