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Obs & Gynae > Normal(ish) Labour > Flashcards

Normal(ish) Labour Flashcards

1
Q

What factors determine progress during labour?

A

Degree of force expelling fetus (the powers)

Dimensions of pelvis and resistance of soft tissues (the passage)

Diameters of fetal head (the passenger)

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2
Q

What happens during contractions?

A

Uterus contracts for 45-60 secs every 2-3 minutes

Cervix pulls up (effacement) and dilates

Poor uterine activity is common in nulliparous women

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3
Q

What are the measurements of the bony pelvis?

A

Inlet = transverse>AP

  • transverse 13cm
  • AP 11cm

Mid-cavity = round
- transverse and AP are equal

Outlet = AP>transverse

  • transverse 11cm
  • AP 12.5cm
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4
Q

What are the main differences of primips?

A

Inefficient uterine action -> long labour
Functional capacity of pelvis not known - possibility of cephalopelvic disproportion
Serious injury to child more common
Uterus virtually immune to rupture

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5
Q

How does the uterus change during pregnancy?

A

Smooth muscle fibres undergo hypertrophy and hyperplasia

Contracts intermittently from beginning of pregnancy, frequency and amplitude increases - most intense at fundus

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6
Q

What are pro-pregnancy factors?

A

Progesterone - produced from corpus luteum for 8 weeks and then placenta
Nitric oxide
Catecholamines
Relaxin

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7
Q

What effect does progesterone have on labour?

A

Decreases uterine oxytocin receptor sensitivity

Promotes uterine smooth muscle relaxation

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8
Q

What is Mifepristone?

A

Progesterone antagonist

Increases myometrial contractility

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9
Q

What are pro-labour factors?

A 
Oestrogens
Oxytocin
Prostaglandins
Prostaglandin dehydrogenase
Inflammatory mediators
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10
Q

What is the role of oxytocin?

A

Nonapeptide
Produced by posterior pituitary
Stimulates uterine contractility
Doesn’t increase towards labour

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11
Q

What is the role of oestrogens?

A

Increase at labour - placenta secretes corticotrophin-releasing hormone
Increase oxytocin receptor expression in uterus

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12
Q

What is the role of prostaglandins?

A 
Double around labour
Synthesised from arachidonic acid by COX enzymes in fetal membrane
Promote cervical ripening
Stimulate uterine contractility
Upregulate oxytocin receptors
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13
Q

How is labour diagnosed?

A

Painful regular contractions -> effacement and dilation of cervix
Accompanied by show (white/pink mucus plug from cervix) +/- rupture of membranes

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14
Q

What is the first stage of labour?

A

From diagnosis to 10cm dilation of cervix

Latent phase - first 3cm take several hours
Irregular contractions, may last 8hrs+ in primips

Active phase - 3-10cm
Contractions are regular, rhythmic and painful
3-4:10 mins
Last 1 mins
12-14hrs in primips
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15
Q

What is the second stage of labour?

A

From full dilation to delivery

Passive stage - until head reaches pelvic floor and woman experiences desire to push

Compression of fetal head and placenta -> vagal response -> transient fall in fetal heart rate

Active stage - pressure of head on pelvic floor produces desire to push
40 mins for nulliparous, 20 mins for multiparous

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16
Q

What is the third stage of labour?

A

From delivery of fetus to delivery of placenta
Lasts around 15 mins and can cause blood loss of 500ml

Uterine muscle fibres contract to compress blood vessels

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17
Q

How much blood is lost during delivery of the placenta?

A

Around 500ml

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18
Q

How is the perineum damaged during delivery?

A

Damaged in 2/3 of nulliparous and half of multiparous women

1st degree - minor damage to fourchette

2nd degree/episiotomy - perineal muscle

3rd degree - anal sphincter

4th degree - anal mucosa

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19
Q

How does the fetus move during the 1st stage of labour?

A

Flexed head as it descends

90 degree rotation from OT to OA/OP position

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20
Q

How does the fetus move during the 3rd stage of labour?

A

Head extends as it is delivered over perineum

Rotates back to transverse before shoulders deliver

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21
Q

What is the station of a fetus?

A

Descent of head of vaginal palpation
Measured in relation to ischial spines
-3 is above spines
+3 is below spines

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22
Q

What causes the cervix to efface?

A

Prostaglandins and glycoproteins weaken collagen fibres of cervix

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23
Q

What is vertex presentation and what is felt?

A

Maximum flexion with bowed head
Presenting diameter of 9.5cm

Anterior fontanelle (bregma)
Sagittal, coronal and lamboidal suture
Posterior fontanelle (occiput)
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24
Q

What is brow presentation and what is felt?

A

Extension of 90 degrees
13cm diameter

Forehead of fetus
Anterior fontanelle (bregma)
Sagittal and coronal suture

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25
Q

What is face presentation and what is felt?

A

Hyperextension of 120 degrees

Face
Part of anterior fontanelle

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26
Q

What is the attitude of the fetus?

A

The relationship between fetal head and spine i.e. flexed, extended

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27
Q

What is the position of the fetus?

A

Relationship of presenting part to maternal pelvis
Must rotate at outlet so sagittal suture lies vertical

Usually occiputo-anterior
Occipito-posterior may cause difficulties

Occipito-transverse means delivery without assistance is impossible

28
Q

What is Ferguson’s reflex?

A 
Descent of presenting part in pelvis
Pressure of presenting part on cervix
Afferent impulse to hypothalamus
Efferent impulses to post pituitary
Post pituitary releases oxytocin
Stimulation of contractions in uterus
Increases pressure on cervix
29
Q

How do contractions occur?

A

Mechanical stretching of uterus stimulates myometrium to make it more responsive
Contractions begin in fundus
Axis of uterus straightens, promotes descent of presenting part

30
Q

What observations are done during labour?

A 
Frequency of contractions - 30 mins
BP and vaginal examination - 1 hour
Pulse - 15 mins
Temp - 4 hours
FHR - 5 mins, after contractions
31
Q

What is the relevance of meconium stained liquor?

A

Sign of fetal distress and risk of meconium aspiration

32
Q

How is delay in first stage of labour managed?

A

Artificial rupture of membranes then reassessment after 2 hours

IV syntocinon then continuous electronic fetal monitoring
REDUCE if >5 contractions/10 mins

STOP if pathological CTG, fresh vaginal bleeding or emergency LSCS

33
Q

What is classified as delay in first stage of labour?

A

Cervical dilatation less than 1cm/hour after 3cm

34
Q

What dose of Syntocinon is used?

A

10 units in 500ml saline
Infuse at 3ml/hr
No more than 36ml/hr for multiparous women

In patients at risk of fluid overload (pre-eclampsia, diabetes, cardiac disease) - make up with 50ml saline

35
Q

What fetal risk factors are associated with poor outcomes?

A

Presence of meconium
Maternal pyrexia
CTG abnormalities

36
Q

What maternal risk factors are associated with poor outcomes?

A

Malposition -> increased perineal trauma

PPH more common in women with long second stage

37
Q

When is continuous fetal monitoring recommended?

A 
Fetal heart baseline 160bpm
Deceleration of the fetal heart
Oxytocic augmentation
Epidural analgesia
Maternal pyrexia, vaginal bleeding, passage of meconium
Active stage >60 mins
38
Q

What are features of uterine dehiscence and rupture?

A 
Abdo pain (constant)
Tachycardia
Vaginal bleeding
Haematuria
Collapse
Fetal bradycardia or decelerations
39
Q

How are epidurals managed during second stage?

A

Associated with increased length of second stage and risk of instrumental delivery
No increase in rate of CS

0.1% bupivacaine with fentanyl

Use syntocinon to reduce risk of instrument delivery

40
Q

Is syntocinon used in multiparous women regularly?

A

NO

41
Q

What is pudendal nerve block?

A

Injection of lidocaine into perineum before episiotomy

42
Q

How much numbness does the pudendal nerve block give?

A

Doesn’t stop:

  • sensation to ant portion of perineum (ilioinguinal and genitofemoral nerves)
  • uterine contraction pains and cervical dilation (T10-L2)
43
Q

What needle is used for pudendal nerve block?

A

Iowa trumpet or Kobak

with 6 inch needle

44
Q

What positions are best to deliver in?

A

Squatting
Kneeling
Left-lateral

Not flat on back as this compresses blood vessels, reduces cardiac output and causes hypotension

45
Q

What is pyrexia in labour and what is the significance?

A

> 37.5
Associated with increased risk of neonatal illness
More common with epidural and prolonged labour

Cultures of vagina, urine and blood are taken
Paracetamol given
Abx if fever reaches 38 or other signs of sepsis

46
Q

How is slow progress of 1st stage of labour treated in nullips?

A

First amniotomy
Wait 1-2 hours and if cervical dilation isn’t furthered then oxytocin

Increases dilatation within 4 hours if it’s going to be effective

47
Q

What are causes of hyperactive uterine activity?

A

Placental abruption
Too much oxytocin
Prostaglandin administration

Excessively strong/frequent/prolonged contractions
Fetal distress as placental blood flow is diminished

Tx: tocolyitc (salbutamol)
C-section

48
Q

How is slow progress of 2nd stage treated in nullips?

A

Passive stage - oxytocin started and pushing delayed for 2 hours

Active stage - if >1hr, spontaneous delivery unlikely due to maternal exhaustion
Episiotomy or ventous/forceps

49
Q

How are OP positions managed during labour?

A

Longer and more painful labour
Many rotate to OA spontaneously
May require C-section or ventouse manual rotation

50
Q

How are OT positions managed during labour?

A

Only significant after 1hr of pushing in 2nd stage

Ventouse to rotate with traction

51
Q

What presentations require C-section?

A

Brow presentation

Face presentation with chin posterior

52
Q

What is cephalo-pelvic disproportion and who does it occur in?

A

Retrospective diagnosis

Large babies
Short women
Head remains high in nulliparous women

53
Q

What is the gynaecoid pelvis?

A

50-80% Caucasian women

Ideal pelvis

54
Q

What is the anthropod pelvis?

A

Narrower inlet

Transverse less than AP

55
Q

What is the android pelvis?

A

Heart shaped inlet

Funnels down to mid-pelvis

56
Q

What is the platpelloid pelvis?

A

Oval shape of inlet persists in mid pelvis

57
Q

What causes abnormal pelvic architecture?

A 
Rickets
Osteomalacia
Poorly healed pelvic fractures
Kyphosis/scoliosis
Poliomyelitis
Congenital malformations

Ovarian tumour
Uterine fibroid

58
Q

What causes damage to the fetus during birth?

A 
Fetal hypoxia - distress
Infection/inflammation
Meconium aspiration -> chemical pneumonitis
Trauma - forceps
Fetal blood loss
59
Q

What pH indicates significant hypoxia?

A

pH less than 7.2 in FBS

60
Q

What causes hypoxia in labour?

A 
Contractions reduce placental perfusion and compress umbilical cord
Placental abruption
Hypertonic uterine state
Use of oxytocin
Prolapse of umbilical cord
Maternal hypotension
61
Q

What is meconium seen in the amniotic fluid?

A

Rare in preterm
Common after 41 weeks

Peasoup meconium increases mortality 4x

62
Q

How is fetal distress managed?

A

Intermittent auscultation of fetal heart - if abnormal or meconium or long labour then

Continuous CTG - sustained bradycardia -> deliver

FBS - if abnormal and >7.2 then repeat after 30 mins

DELIVER

63
Q

What resuscitative measures are taken for fetal distress before FBS and delivery?

A

Woman placed in left lateral position - avoid aortovacal compression

Oxygen and IV fluids

Stop oxytoicin, stop contractions with beta-2 agonists

VE - exclude cord prolapse and very rapid progress

64
Q

How is perinatal infection treated?

A

Screen for organism and treat high risk groups

Low grade maternal fever - RF for seizures, fetal death and cerebral palsy

65
Q

How is meconium aspiration reduced?

A

Amniofusion of saline into uterus

Obs & Gynae (20 decks)

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