Which one of the following hormones is NOT involved in the process...

Parturition is induced by a complex neuroendocrine mechanism involving cortisol, estrogens, and oxytocin.

The signals for parturition originate from the fully developed fetus and the placenta. The fetal pituitary secretes ACTH, which stimulates the fetal adrenal glands to secrete corticosteroids (cortisol). Corticosteroids cross the placenta and alter the estrogen to progesterone ratio, increasing prostaglandin synthesis and stimulating uterine contractions.

The mild uterine contractions (fetal ejection reflex) trigger the release of oxytocin from the maternal posterior pituitary, which causes stronger uterine contractions, leading to the expulsion of the baby.

Human chorionic gonadotropin (hCG) is secreted by the placenta during early pregnancy to maintain the corpus luteum and stimulate it to secrete progesterone and estrogen. It is not involved in the process of parturition.

Answer: hCG