EXHALED CARBON-MONOXIDE AND URINARY COTININE AS MEASURES OF SMOKING IN PREGNANCY

We examined the relationships among self-reported cigarette consumptio n, exhaled carbon monoxide, and urinary cotinine/creatinine ratio in P regnant women. Information on these measures of smoking was collected at firs: and 36th week prenatal visits. Correlations between cigarette consumption and exhaled carbon monoxide were .65 at the first visit a nd .70 at the 36th-week visit. For urinary cotinine/creatinine ratio, the correlations were .61 and .65, respectively, at these visits. Corr elations with change in cigarette consumption between the two visits w ere .37 for change in carbon monoxide and .33 for change in urinary co tinine/creatinine ratio. Urinary cotinine/creatinine ratio had slightl y higher overall agreement with self-reported smoking status and was l ess likely to misclassify smoke rs than carbon monoxide. We conclude t hat urinary cotinine/creatinine ratio is the more accurate measure for validating smoking status among pregnant women, bur exhaled carbon mo noxide is the better measure of cigarette consumption and of changes i n consumption. (C) 1997 Elsevier Science Ltd.