Physiology of Pregnancy

Question 1

What are the 2 theories behind the induction of labour?

Answer 1

1) Placental clock theory
2) Signals from the baby

Question 2

What is the placental clock theory?

Answer 2

1) ^ of CRH from placenta -> foetal ACTH release
2) Release of oestrogens, formation of myometrial gap junctions
3) Regular/Coordinated uterine contractions

Question 3

What is Increased Signals from Baby theory?

Answer 3

1) Increased ACTH/surfactant proteins activate amniotic fluid macrophages
2) Migrate to uterine wall ->Up-regulation of inflammatory gene expression -> Labour stimulated

Question 4

What are the 3 stages of Parturition?

Answer 4

1) Dilation: Cervical remodelling and uterine contractions
2) Expulsion: Full dilation to delivery of infant
3) Placental delivery

Question 5

What 2 drugs can inhibit uterine contractions?

Answer 5

1) Nifedipine - CCB
2) Atosiban -> Oxytocin antagonist

Question 6

Why can nifedipine be used to inhibit premature contractions?

Answer 6

CCB, so can block the rise of intracellular calcium therefore inhibiting muscle contraction.

Question 7

Parturition: what happens in the expulsion phase that triggers myometrial contractions?

Answer 7

Oxytocin release -> increased intracellular Ca2+ -> myometrial contractions.

Question 8

Parturition: do progesterone levels fall when the cervix dilates and remodels?

Answer 8

Progesterone levels don’t fall but it becomes ineffective -> contractions.

Question 9

What are the main hormones in pregnancy?

Answer 9

Main hormones:
hCG, Progestins and Oestrogen
hPL, Prolactin and Oxytocin

Question 10

hCG: Site produced and overall function

Answer 10

Produced: Trophoblast
Function: 1) Signals presence of blastocyst
2) Prevents corpus luteum from dying (Luteal regression)

Question 11

Progestins: Site produced and overall function

Answer 11

Site: Initially C Lutem, after W7 placenta
Function: 1) Prepares endometrium for implantation
2) Promotes myometrial quiescience
3) Increases maternal ventilation

Question 12

How do progestins prepare the endometrium for implantation?

Answer 12

Progestins stimulate the proliferation of cells, vascularisation and the differentiation of endometrial stroma.

Question 13

Oestrogen: Site produced and function

Answer 13

Produced: Initially in the ovary and then from a combination of foetal and maternal sources.
Function: 1) Alters carbohydrate metabolism
2) Promotes change in CV system

Question 14

What is the main oestrogen in pregnancy?

Answer 14

E3; Indicates foetal wellbeing

Question 15

What is the role of E2 in pregnancy?

Answer 15

E2 is responsible for proliferation of the endometrial epithelium. It also facilitates progesterone action.

Question 16

What is the role of human placental lactogen (hPL)?

Answer 16

1.Mobilises glucose from fat.
2.Acts as an insulin antagonist.
3.Converts mammary glands into milk secreting tissues.