OBJECTIVE: To examine the relationship between maternal smoking during pregnancy and the body composition of offspring. SUBJECTS: Grade 4 elementary school children (n ¼ 1366; boys/girls, 724/642; 9 --10 years old) were enrolled in this study. All parents answered a lifestyle questionnaire, and children underwent passive smoking tests. Urinary cotinine measurement and lifestyle screening test parameters (that is, body weight, body length, body mass index (BMI), obesity index (OI), blood tests for liver function and lipid profile and questions regarding maternal smoking and lifestyle) were evaluated in terms of their relationship with maternal smoking. In addition, urinary 8-hydroxydeoxyguanosine (8-OHdG) concentration was measured in 80 randomly selected children to assess its relationship with oxidative stress. RESULTS: Both BMI and OI were significantly higher in children whose mothers smoked during pregnancy than in those whose mothers never smoked (BMI: 17.2±2.7 vs 16.9±2.5 kg m --2 , P ¼ 0.016; OI: 2.7±14.3% vs 0.4±14.0%, P ¼ 0.003). The degree of elevation was positively correlated with the duration of maternal smoking. The increases in BMI and OI resulted from increased body weight and reduced height. The confounding factors---'breakfast with family', 'watching television at dinner', 'eating and drinking before sleep', 'watching television for 42 h', 'sleep duration o8 h' and 'playing sports'---were statistically significant. BMI and OI were significantly high in children whose mothers smoked during pregnancy in these six confounders. On the other hand, urinary 8-OHdG concentration was negatively correlated with BMI in children who had 41.3 ng ml --1 urinary cotinine, suggesting that it may be related to basal metabolism due to oxidative stress. CONCLUSION: Maternal smoking is a risk factor for higher BMI and OI in 9-to 10-year-old children whose mothers smoke during pregnancy and may be independent of other confounding factors.

Maternal smoking during pregnancy may be an independent risk factor of changing body composition in offspring, that is, shorter height and increased weight.

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