Smoking status in pregnant women - Assessment of self-report against carbon monoxide (CO)

Smoking according to self-report and to carbon monoxide (CO) were examined in 7.405 pregnant women who agreed to complete a breath test and questionna ire. The sensitivity and specificity of self-report against CO, and predict ors of a high CO among reported nonsmokers, were examined. The prevalence o f reported smoking was 23% (95% CI: 19.4-26.4), and 20% had a CO of 9 or mo re (95% CI: 17.0-23.1). The sensitivity and specificity against CO were 87% (95% CI: 83.1-91.6) and 93% (95% CI: 91.9-94.6). The positive predictive v alue was 76% (95% CI: 73.2-79.8), reflecting CO's inability to detect light smoking. The negative predictive value was 97% (95% CI: 95.6-97.8). The be st predictors of high CO among reported nonsmokers were being divorced/sepa rated (9.8% had high CO), quitting during pregnancy (8.5% had high CO), bei ng third trimester, and high passive exposure. Some pregnant women may repo rt inaccurately despite validation. Difficulties remain in determining the contributions of passive exposure and inaccurate report to inconsistencies between biochemical and self-report measures. (C) 2000 Elsevier Science Ltd . All rights reserved.