Progesterone
during the first 2 weeks stimulates the fallopian tubes to secrete the nutrients the zygote/blastocyst requires
placenta starts production at 6 weeks and takes over at 12 weeks
progesterone inhibits uterine contractions by
- Inhibiting production of prostaglandins
- Decreasing sensitivity to oxytocin
stimulates development of lobules and alveoli
Oestrogen
oestriol is major oestrogen (not oestradiol)
stimulates the continued growth of the myometrium
stimulates the growth of the ductal system of the breasts
Prolactin
increase during pregnancy probably due to oestrogen rise
initiates and maintains milk secretion of the mammary gland
essential for the expression of the mammotropic effects of oestrogen and progesterone
oestrogen and progesterone directly antagonises the stimulating effects of prolactin on milk synthesis
hCG
secreted by syncitiotrophoblast, stimulated by GnRH produced in adjacent cytotrophoblast
can be detected within 9 days, peak secretion at 9 weeks
mimics LH, thus rescuing the corpus luteum from degenerating and ensuring early oestrogen and progesterone secretion
stimulates production of relaxin
may inhibit contractions induced by oxytocin
Also
Relaxin: suppresses myometrial contractions and relaxes the pelvic ligaments and pubic symphysis
hPL: has lactogenic actions (insignificant with respect to prolactin) - antagonises insulin, therefore making less glucose available to the mother - enhances protein metabolism