Session 10

Question 1

Differentiate between the terms ‘spontaneous abortion’ ‘pre-term’ and ‘term’

Answer 1

Spontaneous abortion - before 24 weeks
Pre-term - before 37 weeks
Term - 37-42 weeks

Question 2

Describe the stages of labour

Answer 2

Latent phase - slow, cervical dilation, variable
Active phase - faster rate of cervical change, regular contractions
1. Creation of a birth canal
2. Expulsion of fetus
3. Expulsion of placenta

Question 3

Describe the processes necessary to create a birth canal and its clinical assessment

Answer 3

Maximum size - 11cm
Expansion of soft tissues (cervix, vagina, perineum)
Structural changes to cervix (cervical ripening) - reduction in collagen, increase in GAGs, reduced aggregation of collagen fibres
Triggered by prostaglandins (PGE2, PGF2)
Generation of force (myometrium) - smooth muscle thickened, intracellular Ca2+ rises, regular action potentials, contractions made more forceful and frequent by prostaglandins and oxytocin
Changes in the cervix - effacement (thins, flattens), dilation (–> 10cm)
Rupture of amnion

Question 4

Describe the function and mechanisms of cervical ripening

Answer 4

Structural changes triggered by prostaglandin 
Reduction in collagen
Increase in GAGs
Reduce aggregation of collagen fibres 
Increased levels of relaxin
Effacement - thins, flattens
Dilation --> 10cm

Question 5

Describe the properties of uterine smooth muscle which facilitate labour

Answer 5

Generation of force
Smooth muscle thickened
Intracellular Ca2+ rises
Action potentials at regular intervals –> equal contraction

Question 6

Explain how prostaglandin release is controlled

Answer 6

Controlled by oestrogen:progesterone ration
Oestrogen > progesterone = prostaglandins
Local hormones - produced in endometrium

Question 7

Describe the normal physiological changes in the neonate which enable independent life

Answer 7

1st breath (trauma, cold stimuli) –> increased pO2, low oulmonary vascular resistance
Fetal circulation –> adult circulation
LA pressure > RA pressure –> foramen ovale closes
Ductus arteriosus sensitive to pO2–> contracts at high pO2
Liver can conjugate billirubin

Question 8

Describe the stage of labour in which the fetus is expelled

Answer 8

Up to 1hr
Urge to ‘bear down’ - increase intraabdominal pressure
Crowning
Birth - head flexes, rotates internally, delivered, head rotates and extends, shoulders route,model over, then body

Question 9

Describe the stage of labour in which the placenta is expelled

Answer 9

10 mins after birth of fetus
Increased effect of uterine contractions –> blood vessels compressed
Reduce haemorrhage
Enhanced by giving oxytocic drug

Question 10

What are Braxton Hicks contractions and when do they occur?

Answer 10

Practice contractions

T3

Question 11

Describe the Ferguson reflex

Answer 11

+ve feedback loop

Mechanical stimulation of cervix –> increased prostaglandins and oxytocin –> more stretch –> more oxytocin

Question 12

Describe the processes which normally limit maternal blood loss after birth

Answer 12

Increased effect of uterine contractions –> blood vessels compressed
Reduce haemorrhage

Question 13

Where is oxytocin produced and stored and what is its mechanism of action?

Answer 13

Produced - hypothalamus
Stored - posterior pituitary
Mechanism - acts on smooth muscle receptors

Question 14

Describe the most common fetal presentation

Answer 14

Longitudinal lie
Flexed
Cephalic presentation

Question 15

Describe the principles of inducing labour

Answer 15

Prostaglandin - increase cervical ripening (creation of birth canal)
Oxytocin - increase contractions

Question 16

Describe the three Ps of labour and that may arise

Answer 16

1. Powers
   Myometrium brachystasis:
   Myometrium fibres contract but only partially relax
   Myometrial muscle does not return to its original size
   Contraction and retraction
   Contractions - 3-4, 10 mins, 60s
2. Passage
   Pelvic bones and pelvimetry
   Soft tissues - cervix, vagina, perineum
   Stretching of fibres of levator ani and thinning of central portion
3. Passenger
   Position:
   Lie - longitudinal/transverse
   Attitude - flexion/extension
   Presentation - frank/full breech, single footing breech, number of passengers, size of passenger
   Problems - induce labour, Caesarian section, forceps delivery, vacuum extraction, post partum haemorrhage, involuted uterus –> shock

Question 17

Define the term ‘parturition’

Answer 17

The expulsion of products of conception after 24 weeks

Question 18

Describe, in principle, how delivery may be facilitated by intervention

Answer 18

Caesarian section
Forceps delivery
Vacuum extraction