One of the most important, functional organs critical to the survival and in utero development of the fetus is the placenta. The placenta provides nutrients, assists in the transfer of waste for ultimate excretion by the mother, and plays an important role in protecting the fetus from maternal immune system attack (Maccani & Marsit, 2009). Another key function of the placenta is to secrete hormones which regulate pregnancy stages and protect the fetus, when possible, from harmful xenobiotic, or foreign, exposures, such as maternal drug use during pregnancy (Sood, Zehnder, Druzin, & Brown, 2006). All of these functions of the placenta, as well as placental gene expression, which is modulated by epigenetic regulation, can be affected by environmental insults (Guo et al., 2008; Sood, et al., 2006). Therefore, many have considered the placenta an important and relatively accessible record or history of in utero exposure and pathology (Maccani & Marsit, 2009).
