Labour Flashcards

1
Q

What is labour?

A

The process whereby the fetus and placenta expelled from the uterus, which normally occurs between 37 and 42 weeks.

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2
Q

When is labour diagnosed?

A

When painful uterine contractions accompany dilatation and effacement of the cervix

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3
Q

What occurs in the first stage of labour?

A

The cervix opens to full dilatation to allow the head to pass through

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4
Q

When is the second stage of labour?

A

Between full dilution and the delivery of the fetus

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5
Q

What is the third stage of labour?

A

From delivery of the fetus to delivery of the placenta

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6
Q

What are the three mechanical factors of labour?

A

[1] The degree of force expelling the fetus (the powers)
[2] The dimensions of the pelvis and the resistance of soft tissues (the passage)
[3] The diameters of the fetal head (the passenger)

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7
Q

How often does the uterus contract during labour?

A

For 45-60 seconds about every 2-3 minutes

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8
Q

What do contractions do?

A

Pull the cervix ip (effacement) and cause dilation, aided by the pressure of the head as the uterus pushes the head down into the pelvis.

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9
Q

When is poor uterine activity common?

A

In nulliparous women and in induced labour

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10
Q

How is the level of descent in the uterus measured?

A

Using the ischial spines as station 0 and how many cm above or below, if it is 2cm below the spines, it is station +2, if it is 2cm above the spines it is station-2.

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11
Q

What factors determine how easily the head fits through the pelvic diameters?

A

The attitude (extension/flexion); the position (rotation) and the size of the head

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12
Q

What attitude is ideal for labour?

A

Maximal flexion, keeping the head bowed, this is called vertex presentation.

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13
Q

Why do you not want the attitude to be extension in labour?

A

A small degree of extension results in a larger diameter.

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14
Q

What is a brow presentations?

A

Extension of the head at 90 degrees

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15
Q

What is a face presentation

A

120 degree extension of the head, with the face looking parallel and away from the body.

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16
Q

What is the position of the head?

A

The degree of rotation of the head on the neck.

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17
Q

What should happen to the position of the head during labour?

A

The head must normally rotate 90 degrees during labour to fit through. It should be delivered with the occiput anterior.

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18
Q

What is moulding?

A

The head can be compressed in the pelvis because the sutures allow the bones to compress together and even overlap slightly

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19
Q

What are the positions that the head can be in?

A

Occipito-transverse (bad, needs assistance)
Occipito-posterior (more difficult to deliver)
Occipito-anterior (good)

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20
Q

What does prostaglandin production do during pregnancy?

A

It reduces cervical resistance and increases the release of oxytocin from the posterior pituitary, which aids stimulation of contractions

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21
Q

What is effacement?

A

When the normal tubular cervix is drawn up into the lower segment until it is flat.

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22
Q

What is the ‘show’ that often accompanies effacement?

A

Pink/white mucus plug from the cervix and/or rupture of the membranes, causing release of liquor.

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23
Q

What is the latent phase of the first stage of labour?

A

Where the cervix usually dilates slowly for the first 3cm and may take several hours

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24
Q

What is the active phase of the first stage of labour?

A

Average cervical dilatation is at the rate of 1cm/h in nulliparous women and about 2cm/h in multiparous women. The active first stage should not normally last more than 12h

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25
Q

What happens to the fetus during the second stage of labour?

A

Descent, flexion and rotation are completed and followed by extension as the head delivers.

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26
Q

What is the passive stage of the second stage of labour?

A

It is from full dilatation until the had reaches the pelvic floor and the woman experiences the desire to push.

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27
Q

How long does the passive stage of the second stage of labour last?

A

It can last a few minutes, but can be much longer

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28
Q

What is the active stage of the second stage of labour?

A

When the mother is pushing.

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29
Q

What causes the urge for the mother to push?

A

The pressure of the head on the pelvic floor produces an irresistible desire to bear down, although epidural analgesia may prevent this.

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30
Q

How long after the active stage of the second stage of labour is the baby normally delivered?

A

On average after 40 minutes (nulliparous) or 20 minutes (multiparous). This can be much quicker but if it is over an hour spontaneous delivery is unlikely

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31
Q

How long does the third stage of labour usually last for?

A

15 minutes

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32
Q

Why does the mother stop bleeding after delivery?

A

Uterine muscle fires contract to compress the blood vessels formerly supplying the placenta, which shears away from the uterine wall.

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33
Q

What is a first degree perineal tear?

A

Involves minor damage to the fourchette.

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34
Q

What is a second degree perineal tear?

A

Tear involving perineal muscle

35
Q

What is a third degree perineal tear?

A

Tear involving the anal sphincter.

36
Q

What is a fourth degree perineal tear?

A

Tear involving the anal mucosa

37
Q

How can you reduce a woman fear of labour?

A

Information, reassurance, accommodating reasonable wishes and, most importantly, not treating labour as a disease

38
Q

Why is fear during labour bad?

A

Fear leads to adrenaline secretion and adrenaline is a potent inhibitor of uterine contractions.

39
Q

What position should pregnant women in labour NOT be in?

A

Flat on their back

40
Q

Are women allowed to eat in labour?

A

It should be discouraged in case general anaesthetic is needed.

41
Q

What observations are taken during labour?

A

Temperature, pulse ad blood pressure

42
Q

What is a partogram?

A

A growth chart-like thing that monitors the dilatation of the cervix ±descent of the head over time. Also records maternal vital signs, fetal heart rate and liquor colour

43
Q

What is hyperactive uterine action?

A

Excessively strong or frequent or prolonged contractions.

44
Q

What is the complication of hyperactive uterine action and why does it happen?

A

Fetal distress occurs as placental blood flow is diminished and labour may be very rapid.

45
Q

How long does it take for oxytocin to work?

A

Oxytocin should increase cervical dilatation within 4h if it is going to be effective.

46
Q

What is augmentation?

A

The artificial strengthening of contractions in established labour.

47
Q

What are the clinical features of occipital-posterior position?

A

Labour is often longer and more painful, with backache and an early desire to push.

48
Q

What are the common causes of failure to progress in labour?

A

Powers: inefficient uterine activity
Passenger: fetal size; disorder of rotation; disorder of flexion
Passage: cephalic-pelvic disproportion; possible role of cervix

49
Q

What is cephalic-pelvic disproportion?

A

The pelvis is simply too small to allow the head to pass through. It is often diagnosed retrospectively after exclusion of other reasons for failure to progress.

50
Q

What are the risk factors for cephalic-pelvic disproportion?

A

Large baby, small woman, high head at term in nulliparous women

51
Q

How do you measure fetal hypoxia??

A

The convention is that a pH below 7.2 in the scalp (capillary) blood indicates significant hypoxia but only below 7.0 can cause neurological damage.

52
Q

What length of labour can increase the risk of hypoxia and why?

A

Contractions temporarily reduce placental perfusion and may compress the umbilical cord, so longer labours and those with excessive time (>1h) spent pushing

53
Q

What are some complications that can cause fetal hypoxia?

A

Placental abruption, hypertonic uterine states and the use of oxytocin, prolapse of the umbilical cord and maternal hypotension

54
Q

What are some risk factors for fetal hypoxia?

A

Long labour, meconium, the use of epidurals and oxytocin; PE, IUGR.

55
Q

What are some investigations that are used to diagnose fetal hypoxia?

A

Colour of the liquor (meconium); fetal heart rate auscultation; CTG; fetal ECG monitoring; fetal blood (scalp) sampling

56
Q

What is meconium?

A

The bowel contents of the fetus that stains the amniotic fluid

57
Q

In what gestation delivery is meconium more common?

A

It is rare in preterm foetuses but common after 41 weeks

58
Q

What does meconium mean?

A

When very diluted it is seldom significant; with undiluted (pea soup) perinatal mortality is increased fourfold.

59
Q

How often is the fetal heart rate auscultated?

A

Every 15 minutes during the first stage and every 5 minutes in the second, with a hand-held Doppler for 60 seconds after every contraction

60
Q

What is the mnemonic for assessing a CTG?

A
Dr: define risk
C: contractions per 10 minutes 
Bra: baseline rate (110-160 beats/minute)
v: variability (>5beats/minute)
a: accelerations (reassuring)
d: decelerations
o: over assessment
61
Q

What are the types of decelerations?

A

Early decelerations, variable decelerations, late decelerations

62
Q

What are early decelerations?

A

Synchronous with a contraction as a normal response to head compression and are therefore usually benign

63
Q

What are variable decelerations?

A

They vary in timing and classically reflect cord compression, which can ultimately cause hypoxia

64
Q

What are late decelerations?

A

They persist after the contraction is completed and are suggestive of fetal hypoxia

65
Q

Are CTG’s accurate?

A

A normal CTG is reassuring but the false-positive rate of abnormal patterns is high, do fetal scalp pH before intervention except in emergencies

66
Q

How do you manage fetal hypoxia?

A

Reposition woman (on left side), oxygen and IV fluids administered; stop oxytocin; vaginal examination

67
Q

Why is meconium bad?

A

It can be aspirated by the fetus into its lungs, where it can cause severe pneumonitis

68
Q

What are the anaesthesia options for obstetric procedures?

A

Spinal anaesthesia; pudendal nerve block; epidural analgesia.

69
Q

What are the risk factors for third and fourth degree tears?

A

Forceps delivery, large babies, nulliparity.

70
Q

What are the criteria for a home birth?

A
Woman's request
'Low risk'
37-41 weeks
Cephalic presentation
Clear liquor
Normal fetal heart rate
71
Q

What score is used to assess the need for induction?

A

Bishops score. The lower the score the more unfavourable the cervix

72
Q

What does Bishops score take into account?

A

The degree of effacement or early dilatation, how long in the pelvis the head is (station) and the cervical position (anterior or posterior)

73
Q

What are the methods of induction?

A

Medical: prostaglandins; oxytocin (after membrane rupture)
Surgical: amniotomy

74
Q

What do prostaglandins do?

A

It either starts labour, or the ‘ripeness’ of the cervix is improved to allow amniotomy.

75
Q

When are prostaglandins most effective?

A

In the evening

76
Q

What is cervical sweeping?

A

Passing a finger through the cervix and ‘stripping’ between the membranes and the lower segment of the uterus

77
Q

What are some fetal indications for induction?

A

High risk situations such as prolonged pregnancy, suspected IUGR or APH, poor obstetric history and prelabour term rupture of the membranes

78
Q

What are some materno-fetal indications for induction?

A

PE, maternal diabetes

79
Q

What are some contraindications of induction?

A

Acute fetal compromise, abnormal lie, placenta praevia or pelvic obstruction such as a pelvic mass or pelvic deformity, previous C section.

80
Q

What are the complications of induction?

A

Labour may not start, increased risk of instrumental delivery and C section. Over activity of the uterus; PPH

81
Q

What are some factors that increase the chance of successful vaginal delivery after a C section?

A

Spontaneous labour; <2 yrs interpregnancy interval; low age and BMI; Caucasian; previous elective C section or vaginal delivery; small fetus

82
Q

How do you diagnose prelabour term rupture of the membranes?

A

Typically, there is a gush of clear fluid, which is followed by an uncontrollable intermittent trickle.

83
Q

What are the risks of prelabour term rupture of the membranes?

A

Cord prolapse is rare; small but definite risk of neonatal infection, which is increased by vaginal examination, the presence of group B strep and increased duration of membrane rupture

84
Q

What are the main causes of fetal distress?

A
Fetal hypoxia/distress
Infection (strep B)
Meconium aspiration (pneumonitis)
Trauma (forceps)
Fetal blood loss