Physiology of Labour Flashcards
Hormones
oxytocin - love melatonin - sleep beta endorphins - transcendence catecholomines - adrenaline and noradrenaline prolactin - mothering cortisol - stress
Oxytocin
- made in hypothalamus, transported along nerve fibres to terminals in the PPG
- increases pain threshold
- secreted in pulses into the bloodstream
- connections with sexual activity, orgasm, birth, breastfeeding, touch, warmth, eating
Melatonin
- released in dark quiet environments
- inhibited by interruption and observation
- works synergistically with oxytocin and also boosts oxytocin levels
Endorphins
(epidural inhibits this)
- naturally occurring opiates
- produced by jets and placenta too
- facilitates release of prolactin, preparing for breastfeeding
- aids in fetal lung maturation
- present in breastmilk
Prolactin
- lactogenic effect blocked by high levels of progesterone in pregnancy
- associated with caring/protective behaviours
Catecholomines
- very high levels inhibit oxytocin release
- reduces blood flow to uterus
- beneifical on baby as increases glucose levels and increases absorption of amniotic fluid from lungs
- baby more alert at birth so helps to establish breastfeeding
- when birth is imminent, instinctive push kicks in
Physiology of preerpation for onset of labour
- oestrogen increases in last weeks, resulting in incrwease of prog
- oxytocin causes cervical ripening
- oestrogen stimulates placenta to release prostaglandins wgich induce production of enzymes that will digest collagen in cervix, helping to soften
Uterine muscles
- 3 muscles = inner layer has longitudinal running muscle fibres, outer has longitudinal and circular & spiral muscle fibres where blood vessels are occluded
- at 20/40, walls thicken and after 25/40, walls thin back to original 10mm
Formation of upper and lower uterine segments
- by end of pregnancy, body of uterus divided into 2 anatomically distinct segments
- upper segment formed from body of uterus
- lower formed from isthmus and service
- in labour, longitudinal fibres in upper segment pull on lower segment, causing it to stretch, this is aided by force of descending presenting part
- a ridge forms between upper and lower segments known as physiological retraction ring
Gap Junctions
(how contractions spread from fundus to bottom of uterus)
=regular contractions start graduallu
-tightentng of myometrial cells begin at 20/40
-GJ are pores in muscle cells, allowing transmissions of molecules
-during preg, muscle cells cannot contract synchronistical
-therefore, higher frequency and strength of contractions
-palpation and fetal movements can stimulate myometrial tightenings
Polarity
-the neuromuscular harmony that prevails between the 2 segments of uterus throughout labour
During each contraction:
- upper pole contracts strongly and retracts to expel fetus
- lower pole contracts slightly and dilates to allow expulsion take place
Latent phase - early phase
- 8 hours primp
- effacement from 3cm -0.5cm
- dilatation 0-5cm
- open bowels more regularly
- vomitting
- blood flow going to uterus
- co ordinating of contraction
active phase
- rapid dilatation
- 5-10cm
- rupture of membranes
6 ways to progress in labour
- cervix moves forward
- cervix ripens
- cervix effaces
- cervix dilates
- fetus descends
- fetus rotates
Cervical Dilatation
- occurs as a result of uterine action and the counter pressure applied by the intact membranes of presenting part or both
- pressure applied evenly to cervix causes fungus to contract and retract
- a well flexed head closely applied to cervix favours efficient dilatation