Passive Smoking Is Associated with Poor Asthma Control during Pregnancy: A Prospective Study of 500 Pregnancies

Asthma and tobacco exposure is common among pregnant women. We investigated the effect of passive and active smoking on asthma control during pregnancy. trimester of pregnancy; data on tobacco exposure were also collected prospectively. The primary outcome was episodes of uncontrolled and partly controlled asthma during pregnancy (defined according to GINA-guidelines).NO (p = 0.01) compared to NS without passive tobacco exposure. The relative risk [RR] of an episode of uncontrolled asthma during pregnancy was 4.5 (95% CI 2.7–7.5: p<0.001) in current and ex-smokers compared with never smokers, and 2.9 (95% CI 1.4–5.9; p = 0.004) in NS-women with passive tobacco exposure compared with NS-women not reporting passive tobacco exposure. Treatment with inhaled corticosteroids, most likely as a marker of more severe asthma, was also associated with a higher risk (RR 8.1, 95% CI 5.1–13.0; p