Physiology of labour Flashcards
Define parturition
Labour and childbirth
What is meant by placental clock?
Predestined lifespan of placenta is up to 42 weeks. After this, reduced release of progesterone from placenta and function decreases
What is meant by the foetal clock?
Baby starts producing oestrogen therefore baby is main decided of when labour begins. Oestrogen produced by adrenal glands in the foetus
Easy way to remember if prostaglandin dilates or contracts?
Vowel= dilator Consonant= contractor
What prostaglandins do oestrogens predominantly make?
F and C (contractor)
What prostaglandings do progesterones predominantly make?
E and I (dilators)
What is cervical ripening?
Cervix changes from cylinder to small circle
Becomes soft and pliable
Mediated by collagenolysis
What is myometrial ripening?
Increased cell to cell adhesion and more production of gap junctions
Causes increased oxytocin receptor expression at fundus
What is the main drive for myometrial ripening
Oxytocin
Prostaglandins enhance this change
What is Ferguson’s reflex?
Oxytocin release in circulation, arrives at fundus
Triggers myometrial contraction
Cranial–> caudal contraction, baby pushed further into cervix
Stretch of cervix causes further increase in oxytocin so more contractions
3 signs of labour
Membrane rupture
The show- release of mucus plug which seals cervix
Painful contractions (lasting >40 seconds and come closer and closer)
What is the danger of a baby that doesn’t deliver 24 hours after membrane rupture
Bacterial infection
Why is backache a symptoms of labour?
Innervation of cervix comes from S3-S4 so stimulates nerve endings in the back
What happens in the first stage of labour?
Cervix effaced and dilates from 0-10cm
Myometrial fibres contract and retract
Upper segment of uterus becomes heaped up whilst lower part passivelt thins
How is first stage of labour divided?
Latent phase: 1-3cm dilation
Active phase: 3-10cm dilation
How quick should dilation occur?
First time mum: 1-3cm per hour
Second etc time mum: 3-6cm per hour
What happens during the second stage of labour?
Uterus and vagina form a continuous tube
Uterine contractions supplemented by voluntary contractions of diaphragm
Pelvic floor muscles stretched backwards
How long should second stage of labour take?
40 mins in first time mum
20 mins otherwise
2 phases of the second stage of labour?
Propulsive phase: from full dilation to presenting part reaching pelvic floor
Expulsive phase: reaching pelvic floor to delivery
What happens during the third stage of labour?
Uterine muscles contract tonically to constrict blood vessels passing between interlacing fibres
Placenta separates as placental bed is constricted to half size and expelled from uterine
How long should third stage of pregnancy take
30 mins: otherwise expect severe haemorrhage
3 factors that affect progression of labour?
The passenger
The passage
The powers
How is babies skull adapted for labour?
Skull bones held by fontanelle, allowing bones to override eachother which reduces dimension of babies head
What is the curve of carus
Passage baby has to follow
What is the best position for labour
Squatting
What is the course of action of mothers pelvis is less than 10 cm
C section
What is platypelloid?
African pelvis
Kidney shaped pelvis causes difficulty is labourn ending in obstructive pregnancies
Can result in fistula
What is shoulder dystocia
Shoulder becomes stucks- 3 minutes before brain damage begins
Function of partogram
Tracks womens progress in labour
Episiotomy
Cuts through vaginal epithelium, perineal skin, bulbocavernosus muscle, superficial and deep muscles
