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

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.

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.

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).

We found that current maternal smoking and maternal secondhand smoke exposure during pregnancy increased the risks of wheeze and asthma in her offspring.