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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
What is face presentation and what is felt?
Hyperextension of 120 degrees Face Part of anterior fontanelle
26
What is the attitude of the fetus?
The relationship between fetal head and spine i.e. flexed, extended
27
What is the position of the fetus?
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
What is Ferguson's reflex?
``` 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
How do contractions occur?
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
What observations are done during labour?
``` Frequency of contractions - 30 mins BP and vaginal examination - 1 hour Pulse - 15 mins Temp - 4 hours FHR - 5 mins, after contractions ```
31
What is the relevance of meconium stained liquor?
Sign of fetal distress and risk of meconium aspiration
32
How is delay in first stage of labour managed?
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
What is classified as delay in first stage of labour?
Cervical dilatation less than 1cm/hour after 3cm
34
What dose of Syntocinon is used?
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
What fetal risk factors are associated with poor outcomes?
Presence of meconium Maternal pyrexia CTG abnormalities
36
What maternal risk factors are associated with poor outcomes?
Malposition -> increased perineal trauma | PPH more common in women with long second stage
37
When is continuous fetal monitoring recommended?
``` 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
What are features of uterine dehiscence and rupture?
``` Abdo pain (constant) Tachycardia Vaginal bleeding Haematuria Collapse Fetal bradycardia or decelerations ```
39
How are epidurals managed during second stage?
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
Is syntocinon used in multiparous women regularly?
NO
41
What is pudendal nerve block?
Injection of lidocaine into perineum before episiotomy
42
How much numbness does the pudendal nerve block give?
Doesn't stop: - sensation to ant portion of perineum (ilioinguinal and genitofemoral nerves) - uterine contraction pains and cervical dilation (T10-L2)
43
What needle is used for pudendal nerve block?
Iowa trumpet or Kobak | with 6 inch needle
44
What positions are best to deliver in?
Squatting Kneeling Left-lateral Not flat on back as this compresses blood vessels, reduces cardiac output and causes hypotension
45
What is pyrexia in labour and what is the significance?
>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
How is slow progress of 1st stage of labour treated in nullips?
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
What are causes of hyperactive uterine activity?
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
How is slow progress of 2nd stage treated in nullips?
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
How are OP positions managed during labour?
Longer and more painful labour Many rotate to OA spontaneously May require C-section or ventouse manual rotation
50
How are OT positions managed during labour?
Only significant after 1hr of pushing in 2nd stage Ventouse to rotate with traction
51
What presentations require C-section?
Brow presentation | Face presentation with chin posterior
52
What is cephalo-pelvic disproportion and who does it occur in?
Retrospective diagnosis Large babies Short women Head remains high in nulliparous women
53
What is the gynaecoid pelvis?
50-80% Caucasian women | Ideal pelvis
54
What is the anthropod pelvis?
Narrower inlet | Transverse less than AP
55
What is the android pelvis?
Heart shaped inlet | Funnels down to mid-pelvis
56
What is the platpelloid pelvis?
Oval shape of inlet persists in mid pelvis
57
What causes abnormal pelvic architecture?
``` Rickets Osteomalacia Poorly healed pelvic fractures Kyphosis/scoliosis Poliomyelitis Congenital malformations ``` Ovarian tumour Uterine fibroid
58
What causes damage to the fetus during birth?
``` Fetal hypoxia - distress Infection/inflammation Meconium aspiration -> chemical pneumonitis Trauma - forceps Fetal blood loss ```
59
What pH indicates significant hypoxia?
pH less than 7.2 in FBS
60
What causes hypoxia in labour?
``` Contractions reduce placental perfusion and compress umbilical cord Placental abruption Hypertonic uterine state Use of oxytocin Prolapse of umbilical cord Maternal hypotension ```
61
What is meconium seen in the amniotic fluid?
Rare in preterm Common after 41 weeks Peasoup meconium increases mortality 4x
62
How is fetal distress managed?
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
What resuscitative measures are taken for fetal distress before FBS and delivery?
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
How is perinatal infection treated?
Screen for organism and treat high risk groups Low grade maternal fever - RF for seizures, fetal death and cerebral palsy
65
How is meconium aspiration reduced?
Amniofusion of saline into uterus

Obs & Gynae (20 decks)

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