An article published in the August issue of the 2012 Archives of General Psychiatry showed a link between prenatal smoking and an increased risk for teen obesity. As little as one cigarette a day during the second trimester led to this finding. Previous studies have shown that prenatal smoking is linked to low birth weight, miscarriage, increased fetal heart rate, still birth, and sudden infant death syndrome. And we all know that smoking increases our risk later in life for emphysema, asthma, lung cancer, heart attacks, strokes and much more.
The mechanism for this finding is not known but hypothesized to be somehow related to a lower size of the amygdala, which the part of the brain that processes emotions and stores memories. Because of the correlation they suspect that the ensuing obesity could be related to an increased appetite for fatty foods. I would not hold my breath on this one!