摘要：Objectives . We examined the relationships among maternal smoking in pregnancy, fetal development, and the risk of asthma in childhood. Methods . We conducted a population-based cohort study, where all 58 841 singleton births were followed for 7 years using nationwide registries. Results . Maternal smoking increased the risk of asthma (adjusted odds ratio = 1.35; 95% confidence interval = 1.13, 1.62 for high exposure). Low birthweight and preterm delivery increased the risk of asthma at the age of 7, whereas being small for gestational age did not. Conclusions . Maternal smoking in pregnancy increases the risk of asthma during the first 7 years of life, and only a small fraction of the effect seems to be mediated through fetal growth. Smoking during pregnancy is a well-established determinant of fetal growth and risk of low birthweight. 1 Maternal smoking in pregnancy may influence the development of the fetal respiratory system, as suggested by findings of a relation between maternal smoking in pregnancy and lung function impairment in newborns. 2– 7 A recent study provided suggestive evidence that low birthweight is a predictor of subsequent childhood asthma. 8 There is also some evidence that maternal smoking increases the risk of childhood asthma. 9– 15 However, little is known about the causal pathway between maternal smoking and the risk of childhood asthma. We therefore assessed the effects of maternal smoking in pregnancy on fetal development and the risk of asthma during the first 7 years of life in a cohort of Finnish children born in 1987. In particular, we examined whether the effect of smoking in pregnancy on the risk of childhood asthma is mediated mainly through reduced fetal growth and duration of pregnancy.
