3.Endocrinology of pregnancy and parturition

Question 1

what are the 4 phases of Parturition?

Answer 1

1. quiescence (inactivity)
   2.activation (the last 6-8 weeks of pregnancy)
   3.stimulation
2. involution (puerperium)

Question 2

which hormone inhibits myometrial activity in phase 1?

Answer 2

progesterone

Question 3

at what phase can Braxton- hicks contractions most likely occur?

Answer 3

phase 1

Question 4

what are the signals of myometrial activity in phase 2?

Answer 4

1. uterine stretch as a result of fetal growth
2. fetal maturation activates the fetal HPA-axis

Question 5

how does fetal maturation activate fetal HPA-axis into activation of labor?

Answer 5

fetal maturity–> fetal hypothalamus–> ↑ CRH–> ↑ ACTH–> cortisol and androgen ↑–> cortisol stimulates surfactant production–> fetus secretes lung surfactant protein (SP-A) into amniotic fluid–> initiation of labor

Question 6

what occurs in phase 3 of parturition?

Answer 6

uterine contractions
cervical dilation
fetal and placenta expulsion
(three stages of labor)

Question 7

what is the endocrine explanation for the myometrial contractions in phase 3?

Answer 7

drop in progesterone and ↑ in estrogen–> enhanced estrogen-dependent CAPs: connexin 43, oxytocin receptor and prostaglandin receptors–> binding of the receptors on the myometrial cell membrane–> IC free calcium ↑–> myometrium contracts

Question 8

what occurs in phase 4 of parturition and what hormone predominantes?

Answer 8

uterine involution
cervical repair
breast feeding

oxytocin–> uterine contractions and milk production