Physiology of Labour

Question 1

Hormones

Answer 1

oxytocin - love 
melatonin - sleep
beta endorphins - transcendence
catecholomines - adrenaline and noradrenaline
prolactin - mothering
cortisol - stress

Question 2

Oxytocin

Answer 2

• 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

Question 3

Melatonin

Answer 3

• released in dark quiet environments
• inhibited by interruption and observation
• works synergistically with oxytocin and also boosts oxytocin levels

Question 4

Endorphins

Answer 4

(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

Question 5

Prolactin

Answer 5

• lactogenic effect blocked by high levels of progesterone in pregnancy
• associated with caring/protective behaviours

Question 6

Catecholomines

Answer 6

• 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

Question 7

Physiology of preerpation for onset of labour

Answer 7

• 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

Question 8

Uterine muscles

Answer 8

• 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

Question 9

Formation of upper and lower uterine segments

Answer 9

• 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

Question 10

Gap Junctions

Answer 10

(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

Question 11

Polarity

Answer 11

-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

Question 12

Latent phase - early phase

Answer 12

• 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

Question 13

active phase

Answer 13

• rapid dilatation
• 5-10cm
• rupture of membranes

Question 14

6 ways to progress in labour

Answer 14

• cervix moves forward
• cervix ripens
• cervix effaces
• cervix dilates
• fetus descends
• fetus rotates

Question 15

Cervical Dilatation

Answer 15

• 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

Question 16

Formation of forewaters and hindwaters

Answer 16

• as lower uterine segment forms and stretches, the chorion becomes detached from it
• an increase in uterine pressure causes this loosened part of sac of fluid to budge down into internal os
• the well flexed head fits into the cervx and cuts of the fluid in front of the head (forewaters)
• hind waters are around the body

Question 17

general fluid pressure

Answer 17

• while membranes remain intact, the pressure of uterine contractions is exerted on the fluid and as fluid is not compressive, the pressure is equalised throughout the uterus and over the fetal body = general fluid pressure
• presenting integrity of membranes optimises oxygen supply to fetus and helps prevent intrauterine and fetal infection