Figure 3From: Comparison of CO breath testing and women's self-reporting of smoking behaviour for identifying smoking during pregnancyMean CO levels for each cigarette category with 95% confidence intervals for all reported smokers (N = 546). The mean CO value for all smokers in each category is shown above the bar. The minimum and maximum CO levels for those smoking <10, 11–20, 21–30 and 30+ cigarettes are, 1–34, 1–35, 4–37 and 13–36 p.p.m. respectively.Back to article page