The body’s stress-regulation system can be broken down into two main parts: the sympathetic adrenal medullary (SAM) system and hypothalamic pituitary adrenal (HPA) system. The SAM system is both fast-acting and responsible for the arousal during stress (think fight-or-flight). The HPA system is more drawn-out, releases cortisol, and works to restore the body after times of arousal.

This study focuses on the HPA system, as the over-activation of the restoration system can cause long-term issues in HPA regulation with excess cortisol release. The hormonal environment is also very important during fetal development, as the fetus is vulnerable and constantly alters based on its hormonal environment. Therefore, this study works off of the assumption that any stress and excess cortisol release (or other stress-hormone interaction) can lead to changes in fetal development. This is the backbone for their conclusion that prolonged pre-natal stress yields predisposition to a variety of disorders in the offspring.