Smoking during pregnancy is a preventable cause of infant morbidity and mortality, yet prenatal smoking is a persistent problem, with an estimated 6–22% of women in high-income countries reporting smoking cigarettes during pregnancy.1 Clinic-based interventions are effective in increasing cessation and improving pregnancy outcomes2; however, delivery of these interventions depends on the ability of providers to assess a woman's smoking status and readiness to quit accurately.

Shipton and colleagues sought to estimate the biochemically validated prevalence of women in need of smoking cessation services. Using a random sample of all 2004 births from the West of Scotland, they compared routinely collected self-reported smoking status of pregnant women at maternity booking (8–12 weeks of gestation) and serum cotinine levels from prenatal screening (15–16 weeks of gestation). They found that maternal self-reported smoking status underestimated smoking prevalence by 25%. The authors' findings are consistent with previously published clinical and observational studies in which maternal …