Tobacco smoke exposure during and after pregnancy may cause maternal, fetal, and infant morbidity and mortality. The purpose of this review is to (a). describe existing methods of measuring active tobacco exposure among pregnant women and (b). illustrate the usefulness of these measures in validating self-reported smoking status among these women. Medline, PsycINFO, and Academic Search Elite were used to identify measures of cigarette smoking exposure, prevalence reports, cessation and validity studies, and research on deception about smoking during pregnancy. Review of the research on smoking cessation among pregnant women since 1966 revealed that 36% of studies (9 out of 25) located used only self-report to assess smoking status. The remaining 16 studies used either significant other reports or at least one type of biochemical test to confirm self-report. Deception rates were reported at baseline only, follow-up only, or both in 15 studies. Three federal agencies in the United States collect data on self-reported smoking during pregnancy. Smoking prevalence rates are inconsistent among these agencies. This article demonstrates that measuring smoking status during pregnancy via self-report alone leads to discrepancies in national prevalence rates, deceptions in clinical practice disclosure, and inconsistencies in research study results. Evaluation studies that confirm smoking status among pregnant women by biochemical methods provide more accurate prevalence rates and lead to the most effective behavioral interventions to achieve cessation. National statistics should carry a disclaimer indicating the likelihood of underestimation. Researchers and clinicians should be trained in best-practice, evidence-based behavioral methods to assess prenatal smoking status and to assist those who desire to quit.