Women were categorized as smokers if they smoked one or more cigarettes per day when 16 or 30 weeks pregnant. Only minimal changes in smoking habits appear after 16 weeks of gestation (27). Smoking was analyzed in two categories (smokers vs. nonsmokers), and also in the ordered categories
0, 1–9, and 10 or more cigarettes per day. Furthermore, nonsmokers were analyzed in two categories; those who stopped smoking before 16 weeks of pregnancy were compared with those who were nonsmokers from the beginning of pregnancy. Caffeine intake was calculated from daily intake of coffee (1 cup = 100 mg), tea (1 cup = 50 mg), chocolate (1 cup = 50 mg), and cola (250 ml = 50 mg). Caffeine intake was analyzed in two categories (