Background The nature of the relationship between maternal tobacco smoking during pregnancy and the occurrence of children's behavioural problems is still a matter of controversy. We tested this association using data collected among a sample of children followed from pregnancy to early adolescence (age 11.5 years), accounting for multiple parents’, children's and family characteristics. Methods Data come from 1424 mother-child pairs participating in the EDEN mother-child cohort set up in France. Using repeated measures (3, 5.5, 8 and 11.5 years) of the mother-reported Strengths and Difficulties Questionnaire, we estimated trajectories of children's emotional and behavioural difficulties. Two aspects of maternal smoking were studied: the timing and the level of use (cigarettes/day) during the first trimester of pregnancy. Multinomial regression models controlled for confounding factors including maternal mental health and socioeconomic characteristics using propensity scores with the overlap weighting technique. Results Contrary to bivariate analyses, in propensity score-controlled regression models, maternal smoking throughout pregnancy was no longer significantly associated with offspring emotional or behavioural difficulties. Maternal heavy smoking (≥10cigarettes/day) remained significantly associated with intermediate levels of overall emotional and behavioural difficulties (OR 1.64, 95%CI 1.04-2.58) and conduct problems (OR 3.05 95%CI 1.22-7.61), as well as with high levels of conduct problems symptoms (OR 2.82 95%CI 0.88-9.06) - although the latter did not reach statistical significance. Conclusions The association between maternal smoking in pregnancy and offspring emotional and behavioural difficulties appears to be largely explained by women's other characteristics. However, maternal heavy smoking appears to be related to offspring behavioural difficulties beyond the role of confounding characteristics. Key messages • The association between maternal smoking in pregnancy and offspring emotional and behavioural difficulties seem largely explained by the family's socio-demographic and behavioural characteristics. • Maternal heavy smoking appears to be related to offspring behavioural difficulties beyond the role of confounding characteristics.

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Introduction Although smoking prevalence has been decreasing worldwide, sustained tobacco cessation remains a challenging goal for many smokers. Nicotine replacement therapy (NRT) products remain among the most widespread type of cessation tobacco aids, along with the more recently introduced electronic cigarette, the efficiency of which is still a matter of debate in the public health community. Objectives This study aims to contribute to the ongoing discussion about effective ways of encouraging tobacco cessation and in particular evaluating the role of the two aforementioned tobacco cessation aids with regard to lasting smoking abstinence in real-life settings. Methods The study is based on the French 2017 Health Barometer, a cross-sectional survey conducted by Santé Publique France. Two distinct outcomes related to tobacco cessation were used: smoking status at 6 months follow-up (yes vs. no) and the duration of smoking abstinence. These two study outcomes were examined respectively among N1 = 2783 and N2 = 1824 participants. All results were weighted based on inclusion probability weights and controlled for propensity scores via overlap weighting (OW), which is appropriate when exposure groups are disparate. Results After adjusting on potential confounders, tobacco cessation at 6 months remains significantly associated with e-cigarette use (OR: 1.50 (1.12-1.99)) and e-cigarette use combined with NRT (OR:1.88 (1.15-3.07)). This association did not reach statistical significance in the long-term analysis, nor did the results of NRT use alone in both analyses. Conclusions Overall, while electronic cigarette use alone and combined with NRT is associated with an increase in the likelihood of smoking cessation, the long-term effects are probably limited. Disclosure No significant relationships.