Parental smoking and respiratory illness in infancy.

The relationship between parental smoking and respiratory illness in a birth cohort of 1180 one-year-old children was examined. Maternal smoking was associated with an increased incidence of lower respiratory illness but there was no statistically significant association between paternal smoking and lower respiratory illness. While children of mothers who smoked suffered more lower respiratory illnesses, their overall risk of respiratory infection was similar to that for children of nonsmoking mothers. The association between maternal smoking and infantile lower respiratory illness persisted when the child's social background, perinatal history, and postnatal diet were taken into account. The findings favour the view that prolonged exposure to cigarette smoke predisposes infants to develop lower respiratory symptoms when they contract a respiratory infection.