PGP and fetal growth restriction: The 11β‐HSD2 can reduce glucocorticoids from entering fetal circulation by inactivating glucocorticoids.[101] P‐gp in the placental trophoblasts can use ATP to pump glucocorticoids back to the maternal circulation.[102] Our previous study confirmed that P‐gp inducer (sodium ferulate) can reverse the effect of caffeine on the fetal/placental weights.[38] This implied that intervention in the placental glucocorticoid barrier has the potential to prevent and treat offspring IUGR and related disorders induced by adverse factors such as caffeine through maternal high glucocorticoid.