Parturition Flashcards
What is effacement?
Thinning of the cervix as it stretches
How does hCG decrease contractility?
inhibits formation of myometrial gap junctions
How is oxytocin involved in labour?
There is a 50-fold increase in oxytocin receptor concentrations in the myometrium and endometrium before the onset of labour
Highest concentrations are found at the top of the uterus
This has a contractile effect by causing increase in MGJ
Which hormones inhibit MGJ
- hCG
- progesterone
- relaxin
Which hormones upregulate MGJ?
- oxytocin
- prostaglandin
- oestrogen
- melatonin
What is the effect of CRH on uterine contractility?
CRH has a dual function. Promotes myometrial quiescence for most of pregnancy and then promotes myometrial contractility after the onset of parturition.
How does CRH indirectly affect uterine contractility?
- stimulates prostaglandin production
- augments the myometrial contractile response to prostaglandin
Describe how fetal HPA function contributes to the process of parturition.
Maternal CRH released by the hypothalamus causes increased release of fetal cortisol from fetal adrenal gland. Fetal cortisol acts on the placenta to decrease progesterone and increase oestrogen production. This results in increased output of prostaglandin from the amnion, chorion and uterus.
Where is CRH produced?
Hypothalamus
Also released by the placenta
What role does cytokines play in parturition?
Stimulates prostaglandin synthesis
What is cervical ripening?
Cervix goes from being hard + rigid + 3cm structure to stretchy and filled with water
What role does interleukins play in parturition?
Increases collagenolytic activity of cervix
What role does NO play in parturition?
stimulates release of PGE2 from fetal membranes
Where is oxytocin produced?
Supraoptic nucleus and paraventricular nucleus of the hypothalamus
Where is oxytocin released?
Posterior pituitary
What is the let down reflex?
Women who are breastfeeding release milk if they hear a baby crying
What is the role of oxytocinase?
Enzyme that rapidly breaks down oxytocin, prevents receptor desensitisation
How does oxytocin prepare the fetus for delivery?
Maternal oxytocin crosses the placenta and reaches the fetal brain. Causes a switch in the action of GABA neurotransmitter from excitatory to inhibitory to silence the brain and reduce its vulnerability to fetal hypoxia.
During uterine contraction, the placenta also contracts, contracting blood supply to the baby and reducing blood supply.
Why is post-term delivery (past 42 weeks) worrying?
Degradation of the placenta causing fetal hypoxia
What is primigravidae?
1st time having a baby
How long should the 2nd stage of labour last for a woman having her 1st baby?
1-2 hours
What is fetal axis pressure?
Pressure from the contractions exerts pressure down the fetal spine to its head, aiding the descent of the baby through the birth canal.
What is valsalva manoeuvre?
Pushing while holding breath and chin on chest
- increases intrathoracic pressure
- reduced venous return to the heart
- reduced cardiac output
- reduced blood pressure
- reduced utero-placental blood flow
