Parturition (mainly in sheep) Flashcards
Why are preterm labours bad?
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
Is giving birth safe?
Half a million maternal death per year.
Is more common in developing areas due to limited health care and lack of trained birth attendants.
How is labour in sheep regulated?
The first thing that happens is fetal cortisol levels rises towards delivery
Maternal progesterone then decreases but oestrogen and maternal prostaglandins increase.
What happens if the sheep has progesterone receptor antagonists?
Induces preterm labour.
What is the stimulus for cortisol increase in sheep?
ACTH secreted from the anterior pituitary of the fetus
What happens to labour in a sheep that has cyclopia?
Hypothalamic/pituitary is not developing and therefore is not producing cortisol and will not deliver.
What does cortisol do in sheep?
Stimulate 17-alpha hydroxylase expression from the trophoblasts in the placena which means progestagens can be used as the substrate of oestrogen synthesis
Why is oestrogen important?
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).
How does the fetus control the timing of its own labour? 6 steps
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.
What organ is cortisol essential for its development?
Lung
What is the experimental model chronically catheterised fetal sheep?
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
Does alcohol inhibit fetal sheep movement?
Yes - they gave a ewe alcohol and it stopped the rapid eye movement and ‘breathing’ of the fetus for a bit
What was removed from the fetal sheep model?
Fetal pituitary, fetal adrenal gland, block fetal hypothalamo-pituitary link
What can be measured/done to the fetal sheep model e.g. start labour?
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
Why is fetal cortisol critical for fetal maturation?
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
What happens to prostaglandins during labour?
PGE2 and PGF alpha increase
PGE2 stimulates dilation of the cervix
PG synthesis inhibitors delay/ inhibit labour
PGF alpha stimulates labour
Human parturition - what happens if the placenta sits in front of the cervix?
Catastrophic bleed - most people will be given a cesaerean.
How is labour regulated in women?
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.
What is the final response to regulate labour in women?
Inflammator type response as final stimulus
In humans what part of the fetus does 17 alpha hydroxylase come from and what does this do?
Adrenal for oestrogen synthesis by trophoblasts in the placenta
What happens in oxytocin knockour mice?
Deliver on time but the pups die of starvation due to no milk let down
What happens in PGF2 alpha knockout mice?
Delayed delivary as there is maintianed progesterone by the CL
What happens in CRH knockouts and PGE2 knockouts?
Delivered on time
What happens in COX-1 knockout?
Delivered late and dead due to this extended gestation
What happens in a cox-2 knockout?
Infertile
