An examination of the misclassification rates of prenatal smoking behaviors throughout each trimester of pregnancy.

Purpose: Smoking during pregnancy is the most modifiable risk factors associated to poor pregnancy outcome (CDC, 2012). Self-reported smoking status has been associated with high misclassification rates (Lawrence et al., 2003). The aim of this research study was to examine misclassification rates of prenatal smoking behaviors during each trimester of pregnancy and evaluate personal characteristics associated with women who misclassify their smoking status. We hypothesized that third trimester self-report would be the most reliable measure of prenatal smoking status. Research Methodology: This study was a secondary analysis of a prospective, multicenter trial of pregnant women. Each trimester, prenatal smoking status was assessed via maternal self-report and validated using preset urine cotinine limits. Nonsmokers were defined by a urine cotinine level of \u3c 100 ng/mL; compared to smokers with a level of \u3e 100 ng/mL Bivariate statistics including the two-sample t-test or chi-square test of association were conducted using SAS version 9.3, with an alpha level of .05 throughout. Results: The present study included 380 women in the first trimester, 271 in the second trimester, and 256 in the third trimester. As pregnancy progressed, there was a decrease in misclassification of smoking status. In the first trimester, 35% of pregnant women self-identified as nonsmokers; however, were biochemically validated as smokers. In the second trimester and third trimesters, 31.9% and 26.6%, respectively, misreported their smoking status. Comparisons among those who did or did not misreport their smoking status, yielded no differences in age, education, or planned pregnancy: however smokers who self-reported as non-smokers were more likely to be non-White (p\u3c.001) and had significantly fewer smokers living in the (p=.043). Conclusion: Misclassification of prenatal smoking status decreases as pregnancy progresses. Biochemical validation of smoking status should be considered when assessing prenatal tobacco use; as misclassification rates remain high throughout each trimester of pregnancy