Validation of Self-Reported Smoking and Environmental Tobacco Smoke through Urine Cotinine in Prenatal Care Visits

Introduction: Cigarette smoking during pregnancy is the most significant modifiable risk factor for adverse fetal outcomes, such as low birth weight and premature birth. Efforts to obtain accurate estimate of smoking prevalence among pregnant woman have been hindered by high rates of misreporting. Cotinine is considered a gold standard measure of exposure to cigarette smoke, but its level in urine and its influence in pregnancy vary in different populations. There is no consensus regarding urine cotinine cutoff point that matches all pregnancies and distinguishes smokers from non-smokers and environmental tobacco exposure (ETS). Purpose: To determine the rate of cigarette smoking by selfreport and the level of urine cotinine in pregnant women in the second trimester. Method: 140 pregnant women were interviewed and one time urine sample was collected during a routine prenatal visit. The samples collected in one university related and three private obstetrics and gynecology clinics in North Alabama. Urine cotinine levels were determined using Calbiotech urinary ELISA kit and standardized based on the level of creatinine. Results: Cigarette smoking rate during pregnancy based on self-report was 15.4%. The mean creatinine-standardized cotinine level was 153.0 (ng/ml) (SD=463.7). The rate of smoking based on the Society for Research on Nicotine and Tobacco (SRNT)’s cutoff point (50 ng/ml) was 26.1%. The sensitivity and specific of self-report were 57.6% and 97.8%, respectively. Conclusion: Relying on self-report to determine the smoking status can result in exposure misclassification. In addition, not considering detection of and intervention for ETS would not be helpful in reducing the adverse pregnancy outcomes related to tobacco smoke. Keywords—tobacco smoke exposure, pregnancy, self-repot, cotinine