Smoking prevalence in early pregnancy: comparison of self-report and anonymous urine cotinine testing

Abstract

Objective. Societal pressures against smoking during pregnancy may lead to a reduction in disclosure of smoking status. The objective of this study was to compare prevalence of smoking at prenatal intake by self-report with anonymous biochemical validation.

Methods. Women receiving care at the Duke Obstetrics Clinic from February 2005 through January 2006 were eligible for evaluation. Self-reported smoking and urine samples were obtained anonymously at prenatal intake. The NicCheck™ I semi-quantitative dipstick was used to detect urinary nicotine, cotinine, and 3-hydroxycotinine. The difference, with 95% confidence interval, between the proportions of smokers by self-report and urine testing was calculated for (1) high-positive vs. low-positive and negative results combined and (2) any positive vs. negative results.

Results. Among 297 subjects, self-reported smoking was 18.2 vs. 14.8% for low-positive and negative results combined with an absolute difference of 3.4%, [−2.9%, 9.6%]. When comparing self-report with any positive result (43.1%), the absolute difference was 24.9%, [17.4%, 32.1%].

Conclusions. Our findings suggest that most pregnant women disclose their smoking and many nonsmokers may have significant second-hand exposure. Universal urinary cotinine screening of pregnant women could aid in appropriately counseling women about second-hand exposure as well as monitoring women at high risk for adverse pregnancy outcomes.

Keywords:

• Tobacco
• pregnancy
• self-report

Acknowledgments

This work was supported by National Cancer Institute grant R01CA089053 and the Charles B. Hammond Research Fund at Duke University. This study was conducted at Duke University Medical Center in Durham, NC.