Interestingly, the percentages of syncytiotrophoblast nuclei positive for the CDK inhibitors p15, p16, and p21 were significantly reduced in the IUGR compared with the normal placentas (P < 0.001, P < 0.01, and P < 0.05, respectively, Fig 1C–E). This evidence concerns the gene CDKN2A and fetal growth restriction.