1. Placental hCG
It is glycoprotein secreted first by trophoblast cells before implantation and later by the placenta. hCG stimulates the corpus luteum to secret large amounts of both estrogen and progesterone which are needed for the growth of endometrium that is necessary for adequate development of placental and fetal tissues
2. Placental progesterone
The placenta by 12-14 weeks of gestation produce enough progesterone to replace the one secreted by corpus luteum. Progesterone from placenta is essential for pregnancy for:
a) Stimulation growth and nutrient secretion from endometrium
b) Inhibition of uterine contraction of the uterus, to prevent premature expulsion of the fetus.
c) Stimulation the breast in preparation for milk production.
d) Immunosuppressive action to prevent rejection of fetus.