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). This evidence concerns the gene PGP and fetal growth restriction.