Evaluating the Accuracy of Self-Reported Exposure to Secondhand Smoke during Pregnancy by Measuring Umbilical Cord Blood Cotinine Concentration

Exposure to secondhand smoke (SHS) during pregnancy leads to fetal and neonatal complications. Since the effect of exposure to tobacco smoke during pregnancy on maternal self-reporting may not be accurate، this study design to evaluate the validity and accuracy of maternal self- reported SHS exposure، using the cord blood cotinine as a biomarker of exposure to tobacco at delivery. This was a cross-sectional study conducted on 108 non-smoking pregnant women. They were divided into two groups based on their reports; smoke exposed (54) and non-exposed groups (54). Exposure to tobacco smoke was assessed during pregnancy by measuring cord blood cotinine and using questionnaires. The umbilical cord blood of newborns was obtained at delivery room to evaluate the amount of cotinine (main metabolite of nicotine) and for estimation of the accuracy of maternal self-reported to SHS exposure، cut-off point Cotinine level of umbilical cord serum that more than 2 ng/ml was considered as positive exposed. The geometric mean cotinine of umbilical cord serum in the exposed group (3. 71±1. 22 ng/ml) was significantly higher than the non-exposed (0. 404±0. 63 ng/ml) (P<0. 0001). There was a strong association between maternal reported SHS exposure and umbilical cord cotinine (Kappa= 98%، P<0. 0001). In addition،the reported SHS exposure had 98% sensitivity، 100% specificity، 100% positive and 98% negative predictive value in comparison to umbilical cord cotinine concentration. This study shows that maternal self-reported SHS exposure is highly accurate. Moreover it seems valid questionnaire. Should be considered as an alternative method for measuring chemical biomarkers، such as cotinine; if the structured questionnaires and accurate interviewing techniques is used.