The effect of active and passive household cigarette smoke exposure on pregnant women with asthma

Background: The article was designed to estimate the effect of active and passive household cigarette smoke exposure on asthma severity and obstetric and neonatal outcomes in pregnant women with asthma. Methods: We used a secondary observational analysis of pregnant women with mild and moderate-severe asthma enrolled in a prospective observational cohort study of asthma in pregnancy and a randomized clinical trial (RCT) comparing inhaled beclomethasone and oral theophylline. A baseline questionnaire detailing smoking history and passive household smoke exposure was given to each patient. Smoking status was confirmed in the RCT using cotinine levels. Data on asthma severity and obstetric and neonatal outcomes were collected and analyzed with respect to self-reported tobacco smoke exposure. Kruskal-Wallis and Pearson χ² statistics were used to test for significance. Results: A total of 2,210 women were enrolled: 1,812 in the observational study and 398 in the RCT. Four hundred and eight (18%) women reported current active smoking. Of the nonsmokers, 790 (36%) women reported passive household smoke exposure. Active smoking was associated with more total symptomatic days (P<.001) and nights of sleep disturbance (P<.001). Among the newborns of active smokers, there was a greater risk of small for gestational age< 10th percentile (P<.001), and a lower mean birth weight (P<.001). There were no differences in symptom exacerbation or outcome between nonsmokers with and without passive household cigarette smoke exposure. Conclusions: Among pregnant women with asthma, active but not passive smoking is associated with increased asthma symptoms and fetal growth abnormalities.