Maternal smoking trajectory during pregnancy predicts offspring's smoking and substance use - The Northern Finland birth cohort 1966 study.

The aim was to characterize the association of maternal smoking trajectory during pregnancy with offspring's smoking, alcohol and substance use behavior. We used the prospective Northern Finland Birth Cohort 1966 study including 11,653 mothers and their offspring followed up from mothers' mid-pregnancy to age of 46 years. Main exposure was number of smoked cigarettes per day at each month of pregnancy. Outcome measures were offspring's smoking, alcohol and drug use at age 14, starting age of smoking, ever-smoking, and smoked pack-years until age 46. Four maternal smoking trajectories during pregnancy were identified with latent class trajectory modelling, namely "non-smokers" (86.0% of mothers), "early quitters" (2.0%), "late quitters" (2.1%), and "consistent smokers" (9.9%). In comparison to non-smokers, all maternal smoking was associated with offspring's increased odds of lifetime smoking adjusted for sex of the child, father's smoking, occupational status and place of residence of family, marital status and mood of mother, and desirability of pregnancy. The consistent smoker's class was associated with offspring's number of smoked pack years by midlife (median [interquartile range]: 8.3 [1.4-17.4] vs. 4.8 [0.0-13.0], p = 0.028), and alcohol use in young age (odds ratio 1.23 [95% confidence interval 1.05-1.43]). Overall, to prevent parent-offspring transmission of smoking, the cessation support should target women planning pregnancy. Negative effects of maternal continuous smoking during pregnancy include all substance use and reach up to offspring's middle age.