PPIB and placental insufficiency: Besides ENG, LEP, and FLT1 identified in this study, STAT3, long non-coding RNA H19, and HoxB7 has been reported to contribute to placental insufficiency IUGR by regulating the invasion and proliferation of trophoblasts by the necroptosis pathway RIPK1 and SIRT2, non-canonical TGF-β signaling pathway or Wnt1_β-catenin pathway [42–44].