American Journal of Epidemiology Advance Access originally published online on July 16, 2007
American Journal of Epidemiology 2007 166(4):490; doi:10.1093/aje/kwm198
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LETTERS TO THE EDITOR |
RE: "DOES MATERNAL SMOKING DURING PREGNANCY HAVE A DIRECT EFFECT ON FUTURE OFFSPRING OBESITY? EVIDENCE FROM A PROSPECTIVE BIRTH COHORT STUDY"
1 School of Population Health, University of Queensland, Brisbane, Queensland 4006, Australia
2 Current affiliation: Saudi Aramco, Riyadh 153, Saudi Arabia 11372
(e-mail: ansarirm{at}yahoo.com)
In a recent study, Al Mamun et al. (1) found that children of women who smoked during pregnancy were 31 percent more likely to be overweight and 42 percent more likely to be obese at age 14 years than their counterparts whose mothers did not smoke while pregnant. The body mass indexes of offspring whose mothers smoked before and/or after pregnancy but not during pregnancy were similar to those of children whose mothers never smoked. It is not clear in the paper exactly how maternal smoking during pregnancy might increase offspring's risk of becoming overweight or obese in their teen years; however, the results were independent of a range of potentially confounding factors and suggest a direct effect of maternal smoking during pregnancy on adolescent overweight and obesity.
In my opinion, the evidence regarding direct effects of maternal smoking during pregnancy on the development of obesity in adult life paints a mixed picture. It is well known that size at birth seems to be associated with the distribution of body fat rather than with total body mass index, on which the findings of Al Mamun et al. (1) are based. It is therefore unlikely that there is one simple explanation for the finding that children of mothers who smoke during pregnancy have an elevated risk of obesity. We need to know more about how smoking affects fetal development. In this respect, the most important finding in the papers by Power and Jefferis (2) and Law et al. (3) seems to be that people whose mothers smoked during pregnancy have a lower birth weight and, independently of birth weight, a higher body mass index in adult life. It may be the adaptations of the fetus to maintain its growth rather than a direct effect of maternal smoking on fetal growth itself that underlie the changes in body composition later in life.
Al Mamun et al. (1) also suggest that their results provide yet another incentive for pregnant women to be persuaded not to smoke and for young women to be encouraged to never take up smoking. However, I am at a loss to understand how this study is going to influence young women to never take up smoking. The longitudinal analysis considered a smaller sample of women and did not take into account young women representative of the Australian population. What about the use of multivariable analysis to explore the range of demographic, social, and lifestyle factors influencing young women's smoking behavior as they move through different stages of their lives, such as leaving their parents' home, attending college or university, marriage, and parenthood? In my opinion, it is important to understand the social contexts and the setting in which young women smoke throughout the different stages of their lives before developing interventions to persuade these women to quit smoking. This article does not address these important issues related to young women's smoking behavior; therefore, suggesting that it can provide an incentive to young women to give up smoking is not practical.
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ACKNOWLEDGMENTS |
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Conflict of interest: none declared.
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References |
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 TOP References |
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- Al Mamun A, Lawlor DA, Alati R, et al. Does maternal smoking during pregnancy have a direct effect on future offspring obesity? Evidence from a prospective birth cohort study. Am J Epidemiol (2006) 164:317–25.
[Abstract/Free Full Text] - Power C, Jefferis BJ. Fetal environment and subsequent obesity: a study of maternal smoking. Int J Epidemiol (2002) 31:413–19.
[Abstract/Free Full Text] - Law CM, Barker DJ, Osmond C. Early growth and abdominal fatness in adult life. J Epidemiol Community Health (1992) 46:184–6.
[Abstract/Free Full Text]
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  A. Al Mamun, D. A. Lawlor, R. Alati, M. J. O'Callaghan, G. M. Williams, and J. M. Najman THE AUTHORS REPLY Am. J. Epidemiol., August 15, 2007; 166(4): 490 - 491. [Full Text] [PDF]
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