Despite this large literature suggesting undesirable outcomes in children exposed to maternal smoking during pregnancy, the underlying biological processes in human are not well understood. Work to better understand the underlying mechanisms of fetal programming is ongoing, and many researchers have focused on how epigenetic mechanisms may play a role in mediating the effects of environmental exposures on future outcomes, such as the physical and behavioral health of the individual in infancy, childhood, and adulthood (Maccani & Marsit, 2009). The understanding of how fetal programming may lead to future health consequences have caused some to adopt an even more expanded theory of fetal programming, namely the “developmental origins of health and disease” or DoHAD (Barker, 2004; Gillman, 2005).
