8: Labour

Question 1

What are the 3 stages of labour?

Answer 1

1. Creation of birth canal
2. Expulsion of foetus
3. Expulsion of placenta

Question 2

What happens in the 1st stage of labour?

Answer 2

Creation of birth canal:

1. Release of structures that normally retain foetus in uterus
2. Dilatation of cervix and its realignment with vagina
3. Expansion of soft tissue (cervix / vagina / perineum)
4. Cervix Ripening

Question 3

When diameter does the birth canal need to be expanded to in the Creation of the Birth Canal

Answer 3

10cm

Question 4

What triggers Cervix Ripening?

Answer 4

Prostaglandins

Question 5

What happens in Cervix Ripening?

Answer 5

1. Reduction in collagen
2. Increase in Glycosaminoglycans (GAGs)
3. Reduction in aggregation of collagen fibres (loosens it)

Question 6

What happens in the 2nd stage of labour?

Answer 6

Expulsion of foetus

Question 7

What happens in the 3rd stage of labour?

Answer 7

Expulsion of placenta and changes to minimise blood loss from mother

Question 8

What are the properties of uterine smooth muscle cells that facilitate labour?

Answer 8

Myometrium

• Smooth muscle: thickens at pregnancy
• Fibres contract, but only PARTIALLY relax

Question 9

How does contraction but only PARTIAL relaxation of the myometrium fibres help in labour?

Answer 9

This shortens fibres and pushes foetus from the top

Question 10

What are the properties of uterine contractions in EARLY pregnancy?

Answer 10

1. Low amplitude
2. Every 30 mins

Question 11

What are the properties of uterine contractions in LATE pregnancy?

Answer 11

1. High Amplitude
2. Lower Frequency
3. Can have Braxton-Hicks contractions

Question 12

What are Braxton-Hicks contractions?

Answer 12

High amplitude contractions every now and then

BUT not strong enough to move foetus into labour

Question 13

What are the roles of uterine contractions? (2 things)

Answer 13

1. Dilate cervix
2. Push foetus through birth canal

Question 14

What hormone makes contractions more frequent?

Answer 14

Oxytocin

Increases APs by lowering the threshold

Question 15

What hormone makes contractions more forceful?

Answer 15

Prostaglandins

Increases Ca2+ per AP

Question 16

What hormone softens the cervix?

Answer 16

Prostaglandins

Question 17

Where are prostagandins produced?

Answer 17

Endometrium

Question 18

What oestrogen : progesterone ratio causes an increase in prostaglandin secretion?

Answer 18

Oestrogen > Progesterone

Oestrogen is prostaglandins friend

Progesterone isn’t because they’re both P’s and he’s salty

Question 19

What does a reduction in progesterone do?

Answer 19

Increases prostanglandin release which in turn:

• Ripens the cervix
• Promotes uterine contractions

Question 20

Where is oxytocin secreted from?

Answer 20

Posterior pituitary (controlled by hypothalamus)

Question 21

What increases oxytocin release?

Answer 21

Afferent impulse from cervix and vagina (postive feedback)

Question 22

What does oxytocin act on?

Answer 22

Smooth muscle receptors:

Increases amount of receptors if oestrogen > progesterone

Basically oxytocin increases sensitivity

Question 23

What hormone promotes labour?

Answer 23

Prostaglandins

Question 24

How is labour artificialy induced with Prostaglandins? (2 things)

Answer 24

Vaginal gel

• Ripens the cervix

Question 25

How is labour artificialy induced with oxytocin?

Answer 25

IV synthetic oxytocin * Increases frequency of contractions

Question 26

What analgesia is used during labour? (3 things)

Answer 26

1. Oxygen / nitrous oxide 2. Paracetamol 3. Spinal anaesthesia

Question 27

What is the foetal orientation determined by? (3 things)

Answer 27

1. Lie 2. Presentation 3. Position

Question 28

What is the foetal Lie?

Answer 28

Relationship of Long Axis of Foetus to Long Axis of Uterus

Question 29

What is the most common foetal lie?

Answer 29

Longitudinal

Question 30

What is the foetal Presentation?

Answer 30

Describes which part of the foetus is adjacent to the pelvic inlet

Question 31

What is the most common foetal Presentation?

Answer 31

Cephalic presentation (head at pelvic inlet)

Question 32

What is the foetal Position?

Answer 32

Describes if the head is flexed or deflexed

Question 33

What is the most common foetal position?

Answer 33

Flexed head

Question 34

How can a foetus be monitored? (2 things)

Answer 34

1. Partogram 2. Cardiotocography

Question 35

What are the stimuli for the establishment of independant life? (3 things)

Answer 35

1. First breath 2. Delivery trauma 3. Temperature change

Question 36

What is the response to the stimuli for the establishment of independant life? (3 things)

Answer 36

1. Reduced pulmoary vascular resistance → Reduced pulmonary arterial pressure → Increased L atrial pressure → Shuts foramen ovale 2. Increased pO2 → constricts ductus arteriosus → establishes adult circulation 3. Sphincter in ductus venosus constricts → all blood entering liver passes through hepatic sinusoids

Question 37

What happens immediately afte the foetus is removed?

Answer 37

Powerful uterine contraction → separates placenta → positions it into upper part of vagina

Question 38

What happens around 10 minutes after foetus is expelled?

Answer 38

Placenta and membranes removed

Question 39

What doe the powerful contractions of the uterus (to separate placenta) do?

Answer 39

Compresses blood vessels → reduces bleeding

Question 40

How can the uterine contractions that reduce bleeding be enhanced?

Answer 40

Oxytocin administration

Question 41

What should be given if the placenta is retained?

Answer 41

IV Oxytocin

Question 42

What are the 3 types of Female Genital Mutilation?

Answer 42

1. Clitoridectomy (removing clitoris) 2. Excision (removing clitoris and labia minora) 3. Infibulation (Narrowing of vaginal opeing through covering seal)