Table 4 The biological functions of hCG during pregnancy

1. Promotion of corpus luteal progesterone production

[6, 9–11, 88]

2. Angiogenesis of uterine vasculature

[19–26]

3. Cytotrophoblast differentiation

[18, 61]

4. Immuno-suppression and blockage of phagocytosis of invading trophoblast cells

[62–67, 89]

5. Growth of uterus in line with fetal growth

[68, 69]

6. Quiescence of uterine muscle contraction

[68, 70–72]

7. Promotion of growth of fetal organs

[30–32, 73–76]

8. Umbilical cord growth and development

[27–32]

9. Blastocysts signals uterine decidua prior to invasion regarding pending implantation

[77–80]

10. hCG in sperm and receptors found in fallopian tubes suggesting pre-pregnancy communication

[81–86]

11. hCG receptors in hippocampus and brain stem, may cause nausea and vomiting in pregnancy

[90, 91]

B. Hyperglycosylated hCG

1. Stimulates implantation by invasion of cytotrophoblast cells as occurs at implantation of pregnancy

[13–16]

2. Stimulates growth of placenta by promoting growth of cytotrophoblast cells

[13, 14, 16, 17]

C. hCG and hyperglycosylated hCG together

1. Drives hemochorial placentation

[87]