Labour Flashcards
What is parturition?
Transition from pregnant to non-pregnant state
What is labour?
Process by which a foetus is expelled from the uterus to the outside world
What is delivery?
Method of expulsion of the foetus
What are the purposes of contractions?
Dilation of the cervix
Pushing the foetus through the birth canal
How many stages of labour are there?
3
What is the first stage labour?
Creation of the birth canal
What is the clinical definition of the first stage of labour?
Interval between the onset of labour and full dilatation of the cervix
How is the first stage of labour divided?
Latent phase
Active phase
What is the latent phase?
Onset of labour with slow cervical dilation
What is the active phase?
Faster rate of change and regular contractions
What is the second stage of labour?
Delivery of foetus
What is the clinical definition of the second stage of labour?
Time between full dilatation of the cervix and delivery of the foetus
What are the 2 parts of the second stage of labour?
Passive
Active
What is passive labour?
Descent and rotation of the head
What is active labour?
Maternal effort to expel the foetus and achieve birth
What is the third stage of labour?
Expulsion of the placenta
What is the clinical definition of the third stage of labour?
Time between completed delivery of the baby and completed delivery of the placenta
How is labour initiated?
Prostaglandins promote cervix ripening
Increase in contractility of myometrium
- increase in prostaglandins - increase calcium release
- increase in oxytocin - lowers threshold for action potentials
Initiates uterine contractions
What is cervix ripening?
Reduction in collagen
Increase in glycosaminoglycans
Increase in hyaluronic acid
What is the effect of progesterone on labour?
Progesterone inhibits contractions
What is the effect of oestrogen on labour?
Increases gap junctional communication between smooth muscle cells - increases contractility
What are the borders of the birth canal?
Posterior = sacral promontory Lateral = ilio-pectineal line Anterior = superior pubic rami
What is special about the myometrium?
When they contract, they only partially relax so there is permanent shortening of the fibres
Forces foetus out of uterus
What controls contractility?
Prostaglandins
- more Ca2+ per action potential
Oxytocin
- more action potentials
- lowers threshold
What are the common foetal presentation descriptors?
Lie
Attitude
Presentation
What is lie?
Relationship of long axis of foetus + uterus
What are the different lie positions?
Longitudinal = foetus in position ready for birth
Transverse = foetus perpendicular to uterus
What is attitude?
Posture of foetus during labour
What is the normal attitude position?
Flexed
What is foetal presentation?
Which part of the body is adjacent to the pelvic inlet
What is the normal foetal presentation?
Head is first
What is breech presentation?
Any other part is nearest pelvic inlet - commonly legs/bum
How can labour be stimulated?
Membrane rupture - stimulates prostaglandin release
Artificial prostaglandins
Synthetic oxytocin
Anti-progesterone agents
How can foetus physiology be monitored during birth?
Foetus monitoring
- heart rate
- movements
Maternal temp
Colour + amount of amniotic fluid
Scalp capillary pH
What is the normal mechanism of labour?
Foetus head flexes Head rotates internallu Crowning = head stretches the muscle + skin Head extended + externally rotates Shoulders rotate Delivery
How can delivery be assisted?
Instruments
- forceps
- vacuum
Caesarean section
What is the risk of instrument delivery?
Nerve palsy
- Erb’s palsy
- Klumpke palsy
What is Erb’s palsy?
Damage to upper part of brachial plexus (C5-7)
Elbow = extended Forearm = medially rotated + pronated Wrist = weakly flexed
What is Klumpke palsy?
Damage to lower part of brachial plexus (C8-T1)
Elbow = extended Forearm = supinated Wrist = flexed
How is the placenta delivered?
Placenta separated by uterine contractions
Powerful contraction - constrict the blood vessels
Blood clotting mechanism activated
What stimulates the neonates first breath?
Trauma
Cold
Light
Noise
What is the effect of the first breath?
Tissue resistance decreases in lungs
Vascular resistance increases - blood flows to lungs
Blood becomes oxygenated - pulmonary pO2 increases
Drop in pressure in RA - foramen ovale closes
Increased pO2 causes muscle walls to contract - ductus arteriosus closes
What causes the ductus venosus to close?
Clamping the umbilical cord
