Flashcards in Repro 10.1 partuition. Deck (48):
'the transition from the pregnant state to the none pregnant state at the end of gestation'
Define labour in medical terms?
'describes partuition when both the cervix and uterus have been remodelled'
After what time is expulsion of products of conception known as partuition?
What is the medical term for expulsion of the products of conception before 24 weeks?
(lay people- miscarriage)
What does pre-term mean?
a foetus born after 24 weeks (but before 36)
What does 'term' mean, in terms of partuition?
partuition between 37-42 weeks.
What does 'post term' mean?
Partuition after 42 weeks.
Why is a baby born a long time (weeks) after the due date dangerous?
It can die in utero (placenta can't manage for the bigger needs, and is only supposed to last for 38 weeks)
Can cause haemorrhage and death of the mother.
Broadly, what are the 3 stages of labour?
1st stage- creation of birth canal
2nd stage- expulsion of the fetus
3rd- expulsion of placenta, contraction of uterus.
When can you first palpate the uterus?
At around 12 weeks.
What terms can be used to describe the position of the fetus during the end of pregnancy?
What does lie mean, with respect to the fetus in labour?
What's the most common?
it compares the relationship of the long axis of the fetus against the long axis of the mother.
Longitudinal lie is the most common.
What does presentation mean, with respect to the fetus in labour?
Which part of the fetus is adjacent to the pelvic inlet.
Most commonly the head, 'cephallic presentation'
What does vertex mean, with respect to the fetus in labour?
The orientation of the presenting part of the fetus,
Eg in cephallic presentation, you can have the minimum diameter, forehead, brow etc.
What is the diameter of presentation of the average fetal head?
What is the diameter of the typical pelvic inlet?
What can help to increase the diameter of the pelvic inlet during pregnancy?
Softening of the pelvic ligments, due to collaginases and prostaglandins.
What is 'Effacement'?
Bringing the external os of the cervix up to meet the internal os.
It is part of cervical ripening.
What is the cervix made up of structurally?
lots of collagen.
this needs to be broken down during labour to allow expulsion of the fetus.
What does ripening involve?
-reduction in the amount of collagen (done by collaginases)
-increase in glycoasaminoglycans
-increase in hyaluronic acid
-reducing aggregation of collagen fibres.
What is the purpose of glycsaminoglycans in cervical ripening?
They fit between the collagen strands, pulling them apart and increasing the surface area for the collaginases to work on
This leads to less rigidity of the cervix
What is the purpose of hyaluronic acid during cervical ripening?
It causes water to come in between the layers of tissue (like a blister)
Increases the area of collaginases etc to work on during cervical ripening.
Which muscle is responsible for generating force during partuition?
How does this happen?
Raises in intracellular Ca2+, which occur due to spontaneous action potentials being formed by pacemaker cells.
The Calcium causes SM contraction.
What happens in early pregnancy, regarding contractions?
You get spontaneous contractions around every 30 minutes, but they are of low amplitude.
What's the name given to the contractions experienced in mid-pregnancy?
Braxton Hick's contractions.
They are of higher amplitude than the contractions experienced in early pregnancy, but occur less frequently.
They shouldnt result in expulsion of the fetus.
What happens to contractions during labour?
Early- variable timing but higher implitude.
Late- frequent contractions of even higher amplitude.
What defines clinical labour? (contractions)
Having contractions lasting at least a minute, 3 times within 10 minutes.
What is the action of prostaglandins on contractions?
Lead to increased intracellular calcium, so make contractions stronger.
What is the action of oxytocin on contractions?
They lower the treshold for action potentials, resulting in more action potentials and therefore a higher frequency of contractions.
What is the main factor involved in controlling prostaglandin and oxytocin levels/effects?
If it is high, more prostaglandins are produced and released, and more oxytocin receptors are presented on the surface of the cells, so sensitivity for oxytocin is increased.
Give some features of prostaglandin.
-locally produced hormone (effects not far from where it is released)
-biologically active lipids.
-mainly produced by the myometirum.
Describe the Ferguson reflex.
Oxytocin is released from the posterior pituitary
It acts on the uterus, causing it to contract
it also stimulated the uterus to produce more porstaglandins, which causes further contraction.
Afferent impulses from the vagina and cervix send signals about the contraction to the brain
This causes further release of oxytocin
(positive feedback mechanism)
What is Barchystasis?
A mechanism where during contraction and relaxtion, the uterus doesn't relax as much as it contracts, therefore there is progressive shortening of the muscle fibres
This leads to the pushing down of the fetus until the presenting part gets pushed into the birth canal, and eventually engages in the pelvis.
When is the cervix said to be fully dilated?
At around 10cm, when 4 fingers can be inserted.
Why is the initiation of labour in HUMANS not fully understood?
It was though that cortisol lead to a fall in progesterone, stimulating oxytocin sensitivity and increased PG release.
But in humans, babies without adrenal glands (therefore without cortisol) have been naturally born.
What is it called if the top of the head presents in the birth canal?
What is it called if a foot appears first in the birth canal?
What is the process by which the fetus is expelled from the mother?
-the head flexes
- the head roates internally(to assume the least diameter)
-head stretches vagina and perineum
-head gets delivered
-head rotates and extends
-shoulders delivered, rest of body delivered.
What was the argument for performing epiostomies?
-to control 'tearing' of the perineum, and prevent involvement of the perineal body.
Why are epiostomies not advised?
naturally, tearing will ordinarily occur along the weakest point. they will also be able to heal better.
By making an incision, the natural reparation cannot happen as well, so it will be weakened and increases the likelihood of fistulae.
What happens in the third stage of labour?
Uterus contracts HARD
This shears off the placenta and leads to it's expulsion
(usually takes around 10 minutes)
After partuition, the uterus contracts. Why is this important?
IT compresses the spiral arteries of the uterus.
This reduces blood loss and post-partum haemorrhage
How can you encourage contraction of the uterus post partuition?
-Giving oxytocic drug
-fundal massage manually
What is the first step in establishing independant life for the neonate?
Taking the first breath.
What factors encourage the neonate to take it's first breath?
How does taking the first breath lead to changes to the neonates circulation?
It causes a dramatic decrease in pulmonary vascular resistance.
This causes a decrease in the pressure of the RA and an increase in the pressure of the LA
(results in the closure of the foreamen ovale)
What event leads to the closure of the ductus venosus?
Clamping of the umbilical cord.