Maternal exposure to smoking and infant's wheeze and asthma: Japan Environment and Children's Study

Background: Evidence regarding independent effects of maternal smoking in different time frames of pregnancy and maternal exposure to secondhand smoke on the development of wheeze/asthma in her offspring is limited. We aimed to investigate the effect of maternal exposure to tobacco smoke on wheeze/asthma development at 1 year of age in her offspring using data from the nationwide birth cohort study in Japan. Methods: Pregnant women who lived in the 15 designated regional centers throughout Japan were recruited. We obtained information about maternal smoking or secondhand smoke status and wheeze/asthma development in the offspring from a self-administered questionnaire. Results: We analyzed 90,210 singleton births. Current maternal smoking during pregnancy increased the risks of wheeze/asthma in the offspring compared with no maternal smoking (wheeze: 1–10 cigarettes/day: adjusted odds ratio (aOR) 1.436, 95% CI 1.270–1.624; ≧11 cigarettes/day: aOR 1.669, 95% CI 1.341–2.078; asthma: 1–10 cigarettes/day: aOR 1.389, 95% CI 1.087–1.774; ≧11 cigarettes/day: aOR 1.565, 95% CI 1.045–2.344). Daily maternal exposure to secondhand smoke during pregnancy also increased the risks of wheeze/asthma in her offspring compared with no secondhand smoke exposure (wheeze: aOR 1.166, 95% CI 1.083–1.256; asthma: aOR 1.258, 95% CI 1.075–1.473). The combination of current maternal smoking during pregnancy and maternal history of allergy increased the risks of wheeze/asthma in her offspring (wheeze: aOR 2.007, 95% CI 1.739–2.317; asthma: aOR 1.995, 95% CI 1.528–2.605). Conclusions: We found that current maternal smoking and maternal secondhand smoke exposure during pregnancy increased the risks of wheeze and asthma in her offspring.