Villous placental tissue, cytotrophoblast and syncytiotrophoblast cells, and regular hCG and hyperglycosylated hCG function. Panel A illustrated blastocyst implantation and engulfment and trophoblast invasion at 3–5 weeks of gestation. Arrows illustrates the biological functions of regular hCG and hyperglycosylated hCG. Mononuclear cells are cytotrophoblast cells, cells with multiple nuclei (black circles) represen syncytiotrophoblast cells. In Panel B villous trophoblast formation and function are illustrated at 6–8 weeks of gestation [44, 54, 114, 115]. Figure illustrates villous trophoblast (anchoring villus and floating villus) growth 5 to 10 weeks of gestation, and invasion of the decidua and myometrium in establishing hemochorial placentation. Panel C illustrates functional hemochorial placentation in floating villus at 10–12 weeks of gestation after invasion is complete [114–118]. Cells with varying numbers of multiple nuclei (black circles) represent villous syncytiotrophoblast (VSyn), mononuclear cells are villous cytotrophoblast (VCyto) and extravillous invasive cytotrophoblast (EVICyto). Arrows shows biological actions of regular hCG and hyperglycosylated hCG.