The mechanisms by which fetal PAH exposure impacts birth outcomes may include the induction of apoptosis after DNA damage, anti-estrogenic effects and binding to human aryl hydrocarbon receptor to induce P450 enzymes to receptors for placental growth factors, resulting in decreased exchange of oxygen and nutrients (Davila et al. 1996; Herbstman et al. 2012; Lutz et al. 1998; Page et al. 2002; Perera 2011). This evidence concerns the gene AHR and pulmonary arterial hypertension.