Parturition (mainly in sheep)

Question 1

Why are preterm labours bad?

Answer 1

High morbidity but survival is 85%.
low birth weight, hearing and visual impairments, motor impairments

It is common 6 - 10% in the developed world

We dont know who is going to go early before they go early and this means you can’t stop it

Question 2

Is giving birth safe?

Answer 2

Half a million maternal death per year.

Is more common in developing areas due to limited health care and lack of trained birth attendants.

Question 3

How is labour in sheep regulated?

Answer 3

The first thing that happens is fetal cortisol levels rises towards delivery

Maternal progesterone then decreases but oestrogen and maternal prostaglandins increase.

Question 4

What happens if the sheep has progesterone receptor antagonists?

Answer 4

Induces preterm labour.

Question 5

What is the stimulus for cortisol increase in sheep?

Answer 5

ACTH secreted from the anterior pituitary of the fetus

Question 6

What happens to labour in a sheep that has cyclopia?

Answer 6

Hypothalamic/pituitary is not developing and therefore is not producing cortisol and will not deliver.

Question 7

What does cortisol do in sheep?

Answer 7

Stimulate 17-alpha hydroxylase expression from the trophoblasts in the placena which means progestagens can be used as the substrate of oestrogen synthesis

Question 8

Why is oestrogen important?

Answer 8

Increase promotes uterine myometrium responsiveness and forms myometrium gap junctions and excitatory receptors (Prostaglandin-F-R, oxytocin-R)

Stimulates secretion of prostaglandin E2 to dilate cervic and progesterone stimulates secretion of myometrial stimulants (prostaglandins F2alpha).

Question 9

How does the fetus control the timing of its own labour? 6 steps

Answer 9

1 - The fetal hypothalamic-pituitary-adrenal axis matures
2 - cortisol levels rise in fetus
3 - stimulates placental 17 alpha hydroxylase
4 - progesterone levels fall
5 - Oestrogen levels rise
6 - Prostaglandin levels increase to stimulate cervix to dilate and uterus to contract = labour.

Question 10

What organ is cortisol essential for its development?

Answer 10

Lung

Question 11

What is the experimental model chronically catheterised fetal sheep?

Answer 11

Put catheters in a fetal sheep in utero and you can measure ECG, limb veins, umbilical veins, artery, trachael pressure, sagital vein, ECOG and amniotic fluid pressure

Question 12

Does alcohol inhibit fetal sheep movement?

Answer 12

Yes - they gave a ewe alcohol and it stopped the rapid eye movement and ‘breathing’ of the fetus for a bit

Question 13

What was removed from the fetal sheep model?

Answer 13

Fetal pituitary, fetal adrenal gland, block fetal hypothalamo-pituitary link

Question 14

What can be measured/done to the fetal sheep model e.g. start labour?

Answer 14

Measure circulating hormones, replace a factor thats been removed, stimulate labour by adding components of fetal HPA to the fetus early or block progesterone using antagonis

Question 15

Why is fetal cortisol critical for fetal maturation?

Answer 15

1 - stimulates maturation of the fetal lung structures and surfactant

2 - Required for function of cardiovascular system and luver glycogen storage

3 - Signals the maturation of the fetus

4 - initiates labour

Question 16

What happens to prostaglandins during labour?

Answer 16

PGE2 and PGF alpha increase

PGE2 stimulates dilation of the cervix
PG synthesis inhibitors delay/ inhibit labour
PGF alpha stimulates labour

Question 17

Human parturition - what happens if the placenta sits in front of the cervix?

Answer 17

Catastrophic bleed - most people will be given a cesaerean.

Question 18

How is labour regulated in women?

Answer 18

Fetal hypothalamic-pituitary-adrenal axis and fetal adrenal maturation has a role for increased availability of substrates for oestrogen synthesis.

CRH is also secreted by placenta and there is no clear change in E2:P4 ratio. There is a gradual increase in stimulatory mediators over inhibitors.

Question 19

What is the final response to regulate labour in women?

Answer 19

Inflammator type response as final stimulus

Question 20

In humans what part of the fetus does 17 alpha hydroxylase come from and what does this do?

Answer 20

Adrenal for oestrogen synthesis by trophoblasts in the placenta

Question 21

What happens in oxytocin knockour mice?

Answer 21

Deliver on time but the pups die of starvation due to no milk let down

Question 22

What happens in PGF2 alpha knockout mice?

Answer 22

Delayed delivary as there is maintianed progesterone by the CL

Question 23

What happens in CRH knockouts and PGE2 knockouts?

Answer 23

Delivered on time

Question 24

What happens in COX-1 knockout?

Answer 24

Delivered late and dead due to this extended gestation

Question 25

What happens in a cox-2 knockout?

Answer 25

Infertile