The study took place in two multi-ethnic health-care sites where the research team had conducted previous studies. The study used a randomized mixed design with 500 women who smoked regularly before pregnancy and who had been abstinent for > 30 days at their 28th week of pregnancy. The primary outcome was abstinence at one year postpartum. Secondary outcomes were partner smoking status and exposure of the index baby. Self report was validated biochemically in samples of mothers and babies. The study design separated data collection from the experiments by enrolling subjects in a university-sponsored study of new mothers' health-care site.