Maternal tobacco smoking during pregnancy and children's emotional and behavioural trajectories : The EDEN mother-child birth cohort study.

The relationship between maternal smoking during pregnancy (in 2 modalities: timing and level of smoking) and behavioural difficulties in children is still a matter of debate. While the relationship between any maternal tobacco use and offspring behavioural difficulties appears to be largely explained by confounding factors, heavy maternal smoking in the first trimester of pregnancy seems to be associated with offspring behavioural difficulties beyond the socioeconomic and mental health characteristics transmitted across generations.