Estimation of environmental tobacco smoke exposure during pregnancy using a single question on household smokers versus serum cotinine.

Environmental tobacco smoke (ETS) exposure has been studied in relation to many diseases. The ability of a study to find an association between exposure and disease is, in part, determined by the accuracy of the exposure measure. This study examined how accurately one question, the number of smokers in the household, asked at birth, predicts ETS exposure in pregnant nonsmokers as assessed by serum cotinine.