Onset and management of parturition Flashcards
What are the stages of labour? (4)
Latent
1 - regular contractions, effacement, dilation
2- full dilation, birth
3 - placenta
What do Braxton Hicks contractions do?
Prepare uterine muscle for labour and assist in effacement
Give 3 factors that make labour happen
Activation of myometrium Placental steroids PGs Oxytocin Inflammatory processes \+ve biofeedback mechanisms
Describe/draw the oxytocin +ve feedback loop
Baby pushes against cervix stretching it Nerve impulses to brain Posterior pituitary stimulated to release oxytocin Oxytocin causes uterine contractions Etc
What is happens in myometrial quiescence? (2)
Significant proliferation and hypertrophy of smooth muscle
Capacity for contractility decreased
Give 3 factors that decrease the capacity for contractility
HCG (stops MGJ formation) Progesterone (stops oestrogen) CRH Relaxin Oxytocin (increases relaxatory PGs) Melatonin (suppresses myometrial oxytocin receptors)
What causes activation of the myometrium? (3)
Uterine stretch
Increased oxytocin receptors in endometrium and myometrium
Foetal-hypothalamic-pituitary adrenal axis and increased cortisol
What are MGJs?
Symmetrical portions of plasma membrane from adjacent cells that form intracellular channels for the rapid propagation of action potentials between cells
What is the formation of MGJs stimulated by? (3)
Oestrogen
Prostaglandin
Melatonin
What is the formation of MGJs inhibited by? (3)
Progesterone
hCG
Relaxin
What is fundal dominance?
Increased number of MGJs in fundus
Progressive conductance of electrical activity to cervix
Give 2 possible purposes of CRH
Direct effects on myometrium
Indirect effects by stimulating PG production
Augmenting contractile response to PGE2 and oxytocin
How does the foetus trigger the onset of parturition? (3)
Increased cortisol from foetal adrenal gland
Cortisol acts on placenta to cause decreased progesterone and increased oestrogen
Increased stimulatory PGs from uterus
What do cytokines do in labour? (3)
Stimulate the synthesis of PGs
Interleukins increase collagenolytic activity in cervix
NO stimulates release of PGE2
Where is oxytocin produced?
Hypothalamus
Where is oxytocin released from?
Posterior pituitary
What are the actions of oxytocin?
Indirectly inhibits release of adrenocorticotrophic releasing hormone and cortisol Direct action on myometrium Indirect action on PG production Uterotonic Emotional well-being and bonding
What is oxytocin regulated by?
Oxytocinase
Enzyme that rapidly degrades oxytocin to prevent receptor desensitisation during prolonged oxytocin release
What is the action of oxytocin on foetal neurons?
GABA from excitatory to inhibitory
Silences foetal brain for delivery and reduces vulnerability to hypoxic damage
What is the general maximum duration for the second stage of labour?
Primi - 2 hours
Multi - 1 hour
What occurs in cervical effacement? (3)
Shortening of cervix
Solubility of collagen changes
Forms lower uterine segment
What happens to the uterine muscle fibres in labour?
Contract and retract, gradually shortening
What are the 3 aspects of the second stage of labour?
Power
Passage
Passenger
What is the valsalva manoeuvre?
Closed glottis and holding breath
