MTOR and fetal growth restriction: Placental GLUT1 and GLUT3 expression is downregulated by treating pregnant rats with synthetic glucocorticoids (Hahn et al., 1999), and excessive glucocorticoid concentrations caused by stress or exogenous administration in pregnant rats resulted in IUGR probably by altering placental glucose transport and upregulation of the mTOR signaling pathway (Vaughan et al., 2015).