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A new study has linked smoking during pregnancy with increased risk of obesity in adolescence of the babies of these women. According to the study it is possible mother's habit may lead to subtle structural variations in the brain causing children to prefer fatty foods in young adulthood.

"Prenatal exposure to maternal cigarette smoking is a well-established risk factor for obesity, but the underlying mechanisms are not known," the authors write as background information, according to Medical Xpress. "Preference for fatty foods, regulated in part by the brain reward system, may contribute to the development of obesity." 

For the study, the researchers from Toronto, Canada, studied 378 adolescents aged between 13 and 19 from selected from high schools in Canada.

The participants of the study were divided into groups of those who were exposed to maternal smoking (smoking by pregnant women) and those who were not. Participants in both groups, at the time of the recruitment for the study, were matched by maternal education and his/her school attendance, in order to reduce any influence of socioeconomic status. 

According to the researchers, children who were exposed to maternal smoking were those whose mothers smoked more than one cigarette a day during the second trimester of pregnancy, and the non-exposed were those whose mother who did not smoke for at least one year before (and throughout) the pregnancy, Medical Xpress reported.

The analysis of the study found that exposed participants were marginally heavier and had significantly higher total body fat when compared to non-exposed participants. 

These differences prevailed even after taking to consideration the age, sex, and height and other factors like lower birth weight, shorter duration [or lack of] breastfeeding, etc.

Also, exposed exhibited a significantly lower volume of the amygdala (part of the brain that plays a role in processing emotions and storing memories) when compared to non exposed participants.

According to authors amygdala volume correlates inversely with fat intake. 

"Prenatal exposure to maternal cigarette smoking may promote obesity by enhancing dietary preference for fat, and this effect may be mediated in part through subtle structural variations in the amygdala," the authors conclude.

The study was published Online First by Archives of General Psychiatry.