It was further found that the mRNA and protein expression levels of placental P-gp (ABCB1) were significantly reduced, and the cortisol concentrations of the placenta and fetal cord blood were increased in the IUGR group, and there was no significant difference between males and females (P<0.05, P<0.01, Fig. 1C–F). Here, ABCB1 is linked to fetal growth restriction.