8: Labour Flashcards
What are the 3 stages of labour?
- Creation of birth canal
- Expulsion of foetus
- Expulsion of placenta
What happens in the 1st stage of labour?
Creation of birth canal:
- Release of structures that normally retain foetus in uterus
- Dilatation of cervix and its realignment with vagina
- Expansion of soft tissue (cervix / vagina / perineum)
- Cervix Ripening
When diameter does the birth canal need to be expanded to in the Creation of the Birth Canal
10cm
What triggers Cervix Ripening?
Prostaglandins
What happens in Cervix Ripening?
- Reduction in collagen
- Increase in Glycosaminoglycans (GAGs)
- Reduction in aggregation of collagen fibres (loosens it)
What happens in the 2nd stage of labour?
Expulsion of foetus
What happens in the 3rd stage of labour?
Expulsion of placenta and changes to minimise blood loss from mother
What are the properties of uterine smooth muscle cells that facilitate labour?
Myometrium
- Smooth muscle: thickens at pregnancy
- Fibres contract, but only PARTIALLY relax
How does contraction but only PARTIAL relaxation of the myometrium fibres help in labour?
This shortens fibres and pushes foetus from the top
What are the properties of uterine contractions in EARLY pregnancy?
- Low amplitude
- Every 30 mins
What are the properties of uterine contractions in LATE pregnancy?
- High Amplitude
- Lower Frequency
- Can have Braxton-Hicks contractions
What are Braxton-Hicks contractions?
High amplitude contractions every now and then
BUT not strong enough to move foetus into labour
What are the roles of uterine contractions? (2 things)
- Dilate cervix
- Push foetus through birth canal
What hormone makes contractions more frequent?
Oxytocin
Increases APs by lowering the threshold
What hormone makes contractions more forceful?
Prostaglandins
Increases Ca2+ per AP
What hormone softens the cervix?
Prostaglandins
Where are prostagandins produced?
Endometrium
What oestrogen : progesterone ratio causes an increase in prostaglandin secretion?
Oestrogen > Progesterone
Oestrogen is prostaglandins friend
Progesterone isn’t because they’re both P’s and he’s salty
What does a reduction in progesterone do?
Increases prostanglandin release which in turn:
- Ripens the cervix
- Promotes uterine contractions
Where is oxytocin secreted from?
Posterior pituitary (controlled by hypothalamus)
What increases oxytocin release?
Afferent impulse from cervix and vagina (postive feedback)
What does oxytocin act on?
Smooth muscle receptors:
Increases amount of receptors if oestrogen > progesterone
Basically oxytocin increases sensitivity
What hormone promotes labour?
Prostaglandins
How is labour artificialy induced with Prostaglandins? (2 things)
Vaginal gel
- Ripens the cervix
How is labour artificialy induced with oxytocin?
IV synthetic oxytocin
- Increases frequency of contractions
What analgesia is used during labour? (3 things)
- Oxygen / nitrous oxide
- Paracetamol
- Spinal anaesthesia
What is the foetal orientation determined by? (3 things)
- Lie
- Presentation
- Position
What is the foetal Lie?
Relationship of Long Axis of Foetus to Long Axis of Uterus
What is the most common foetal lie?
Longitudinal
What is the foetal Presentation?
Describes which part of the foetus is adjacent to the pelvic inlet
What is the most common foetal Presentation?
Cephalic presentation (head at pelvic inlet)
What is the foetal Position?
Describes if the head is flexed or deflexed
What is the most common foetal position?
Flexed head
How can a foetus be monitored? (2 things)
- Partogram
- Cardiotocography
What are the stimuli for the establishment of independant life? (3 things)
- First breath
- Delivery trauma
- Temperature change
What is the response to the stimuli for the establishment of independant life? (3 things)
- Reduced pulmoary vascular resistance → Reduced pulmonary arterial pressure → Increased L atrial pressure → Shuts foramen ovale
- Increased pO2 → constricts ductus arteriosus → establishes adult circulation
- Sphincter in ductus venosus constricts → all blood entering liver passes through hepatic sinusoids
What happens immediately afte the foetus is removed?
Powerful uterine contraction → separates placenta → positions it into upper part of vagina
What happens around 10 minutes after foetus is expelled?
Placenta and membranes removed
What doe the powerful contractions of the uterus (to separate placenta) do?
Compresses blood vessels → reduces bleeding
How can the uterine contractions that reduce bleeding be enhanced?
Oxytocin administration
What should be given if the placenta is retained?
IV Oxytocin
What are the 3 types of Female Genital Mutilation?
- Clitoridectomy (removing clitoris)
- Excision (removing clitoris and labia minora)
- Infibulation (Narrowing of vaginal opeing through covering seal)
