Maternal smoking during pregnancy and childhood obesity

A recent cohort study suggested that maternal smoking during pregnancy might be a risk factor for childhood obesity. Data from the obligatory school entry health examination in six Bavarian (Germany) public health offices in 1999-2000 were used to assess the relation between maternal smoking during pregnancy and childhood obesity (n = 6,483 German children aged 5.00-6.99 years). A body mass index greater than the 90th percentile was defined as overweight, and a body mass index greater than the 97th percentile was defined as obesity. The main exposure was maternal smoking during pregnancy. The prevalences of overweight and obesity, expressed as percentages, increased in the following order: never smoked (overweight: 8.1, 95% confidence interval (CI): 7.2, 9.0; obesity: 2.2, 95% CI: 1.7, 2.7); less than 10 cigarettes daily (overweight: 14.1, 95% CI: 11.1, 17.7; obesity: 5.7, 95% CI: 3.7, 8.2); and 10 or more cigarettes daily (overweight: 17.0, 95% CI: 10.1, 26.2; obesity: 8.5, 95% CI: 3.7, 16.1). The adjusted odds ratios for maternal smoking during pregnancy were 1.43 (95% CI: 1.07, 1.90) for overweight and 2.06 (95% CI: 1.31, 3.23) for obesity. A dose-dependent association between overweight/obesity and maternal smoking during pregnancy was observed that could not be explained by a wide range of confounders, suggesting that intrauterine exposure to inhaled smoke products rather than lifestyle factors associated with maternal smoking accounts for this finding.