Maternal smoking during pregnancy increases the risk of recurrent wheezing during the first years of life (BAMSE)

BACKGROUND: Exposure to cigarette smoking during foetal and early postnatal life may have implications for lung health. The aim of this study was to assess the possible effects of such exposure in utero on lower respiratory disease in children up to two years of age. METHODS: A birth cohort of 4089 newborn infants was followed for two years using parental questionnaires. When the infant was two months old the parents completed a questionnaire on various lifestyle factors, including maternal smoking during pregnancy and after birth. At one and two years of age information was obtained by questionnaire on symptoms of allergic and respiratory diseases as well as on environmental exposures, particularly exposure to environmental tobacco smoke (ETS). Adjustments were made for potential confounders. RESULTS: When the mother had smoked during pregnancy but not after that, there was an increased risk of recurrent wheezing up to two years' age, ORadj = 2.2, (95% CI 1.3-3.6). The corresponding OR was 1.6, (95% CI 1.2-2.3) for reported exposure to ETS with or without maternal smoking in utero. Maternal smoking during pregnancy but no exposure to ETS also increased the risk of doctor's diagnosed asthma up to two years of age, ORadj = 2.1, (95% CI 1.2-3.7). CONCLUSION: Exposure to maternal cigarette smoking in utero is a risk factor for recurrent wheezing, as well as doctor's diagnosed asthma in children up to two years of age.