Effects of in utero and environmental tobacco smoke exposure on lung function in boys and girls with and without asthma

To investigate whether the effects of in utero exposure to maternal smoking and environmental tobacco smoke (ETS) exposure on lung function vary by se x or asthma status, we examined medical history and tobacco smoke exposure data for 5,263 participants in the Children's Health Study. At study enroll ment, parents or guardians of each subject completed a questionnaire, and l ung function was measured spirometrically with maximum forced expiratory fl ow-volume maneuvers. To assess the in utero effects of maternal smoking and ETS exposure on lung function, we used regression splines that accounted f or the nonlinear relationship between pulmonary function, height, and age. In utero exposure to maternal smoking was independently associated with def icits in lung function that were larger for children with asthma. Boys and girls with a history of in utero exposure to maternal smoking showed defici ts in maximum midexpiratory flow (MMEF) and a decrease in the FEV1/FVC rati o. As compared with children without asthma, boys with asthma had significa ntly larger deficits from in utero exposure in FVC, MMEF, and FEV1/FVC, and girls with asthma had larger decreases in FEV1/FVC. The effect of ETS expo sure varied by children's gender and asthma status. Deficits in flows assoc iated with current ETS exposure were present in children with and without a sthma but were significant only among children without asthma. Past ETS exp osure was associated with reduced FEV1, MMEF, and FEV1/FVC among boys with asthma. In contrast, past ETS exposure was associated with decreased flow r ates in girls without asthma. In summary, both in utero exposure to materna l smoking and ETS exposure were associated with persistent deficits in lung function. The effects of in utero exposure were greatest among children wi th asthma.