Intrapartum

Question 1

AFE (amniotic fluid embolism)

Answer 1

Rare 1-2:100,000
20% maternal mortality, 80% maternal morbidity (usually neurological) and high fetal mortality

Pathophysiology: when amniotic fluid and associated debris enters maternal circulation causing anaphylactic type reaction causing cardiogenic shock, respiratory failure and inflammation

Amniotic fluid and fetal squamous cells enter circulation -> vasospasm of pulmonary vessels -> pulm HTN -> RV failure -> LV failure -> cardiogenic shock
Fetal cells trigger coagulation cascade causing systemic inflammation and DIC

Risk factors:

• Usually unpredictable and unpreventable
• Precipitous labour
• Polyhydramnios
• IOL with ARM/synto
• AMA
• CS or instrumental
• Praevia or abruption
• Grand multip
• Cervical lacerations
• Fetal distress
• Uterine rupture
• Miscarriage
• Amniocentesis

Clinical presentation:

• Usually in labour or immediately postpartum
• SOB
• Chest pain
• Dizziness
• Hypotension
• Hypoxia and resp distress
• Pulmonary oedema
• DIC
• Seizure
• Fetal distress (if not delivered)
• Eclampsia

Diagnosis:

• Acute maternal collapse with one or more of:
• > acute fetal compromise
• > cardiac arrest
• > arrhythmias
• > coagulopathy
• > hypotension
• > maternal haemorrhage (occurs later due to coagulopathy)
• > seizure
• > SOB
• > hypoxia

Ix:

• DIC screen
• CXR
• ECG

Management:

• Supportive
• IVF, O2
• Regular temp
• Inotropes
• Careful fluid management
• Correct coagulopathy (cryo/FFP/plts)
• Delivery

Question 2

Breech

Answer 2

Incidence of breech is 3-4% at term
90% breech now delivered by CS (changed by Term Breech Trial)

Term breech trial = reduced perinatal morbidity and mortality in planned CS compared to planned breech (1.6% VS 5%), no difference in maternal morbidity, no long term differences in death/neurodevelopmental delay; however criticised for methodological grounds (stopped early, lack of adherence to inclusion criteria, units without access to CS <1hr, CTG optional, no experienced MO at delivery, allocation bias, power)

Meta-analysis 2016 = risk of perinatal mortality 1:333 vaginal breech birth, 1:2000 CS
“The effect of term breech trial on medical intervention” - 175 CS required to avoid 1 fetal death

Prevention of breech = abdominal palpating in antenatal appointments, US if suspected breech

Management = growth US (look for causes including fetal anomaly, placenta praevia)
Offer ECV (after 36wks) if appropriate (need access to emergency CS); 1:200 require emergency CS for abruption/cord prolapse/fetal distress; success rate 40% P0 and 60% multip

Contraindications to ECV = absolute (APH last 7 days, abnormal CTG, SROM, multiple pregnancy except delivery of 2nd twin), relative (SGA with abnormal dopplers, oligo, proteinuric PET, major fetal anomalies, scarred uterus, unstable lie, uterine anomaly)

Factors associated with successful ECV = parity, BMI (less successful BMI>30), placenta (less successful anterior), liquor (less successful oligo, not recommended in poly due to risk of cord prolapse/SROM/underlying fetal anomaly), gestation if primip (less successful greater gestation), fetal position (less successful if engaged or footling breech), fetal weight (less successful macrosomia), uterine relaxation (less successful if tocolysis not used), fetal or uterine anomaly (less successful and contraindicated if present)

For planned vaginal breech, ensure woman is appropriately counselled, clear protocols for case selection and management, CEFM, availability for emergency CS, experienced MO to manage birth, staff regularly trained.

Elective CS recommended for preterm breech after 25wks and anticipate risk of head entrapment. From 22-25+6, CS not routinely recommended for spontaneous preterm labour.

Contraindications to vaginal breech = cord presentation, non frank or complete, IUGR or macrosomia, clinical inadequate maternal pelvis, fetal anomaly incompatible with vaginal delivery, hyperextended neck on US

IOL not recommended, augmentation also not recommended as adequate progress may be best evidence for adequate fetopelvic proportions, only augment if contraction frequency is low with epidural

Maximum 5mins from buttocks to head and 3mins from umbilicus to head.
Head entrapment vaginal breech = cervical incisions at 2,6 and 10 o’clock
Head entrapment CS = J incision or inverse T incision

Question 3

Maternal collapse

Answer 3

Rare but life-threatening event
From antepartum to 6wks postpartum

Changes in pregnancy that affect resus:

• Cardiovascular - increased cardiac output and blood flow to uterus, aortocaval compression
• Respiratory - higher RR and O2 consumption, reduced functional capacity, more difficult to ventilate
• Upper airways - laryngeal oedema, weight gain, difficult to ventilate
• Aspiration - delayed gastric emptying, increased intrabdominal pressure due to gravid uterus, risk of aspiration pneumonitis

Causes of collapse
OBSTETRIC:
- Haemorrhage (most common cause)
- AFE
- Uterine rupture
- Uterine inversion
- Abruption
- Eclampsia
NON-OBSTETRIC:
- Thrombus (most common direct cause)
- Anaphylaxis
- Cardiac (most common indirect cause) - arrhythmia, MI, cardiomyopathy, aortic dissection
- Hypoglycaemia
- Sepsis
- Splenic artery rupture
- Intracranial haemorrhage
- Drug overdose

Also 4H’s (hypoxia, hypovolaemia, hypo/hyperkalaemia, hypothermia) and 4T’s (thrombus, tamponde, tension pneumothorax, toxins)

Management:
- DRABCD
- Tilt 15 degrees onto left
- Airway – intubate as soon as possible (airway more vulnerable because of increased risk of aspiration)
- Breathing – administer high flow oxygen using bag & mask ventilation until intubation can be achieved
- Circulation:
In the absence of breathing, commence CPR immediately (30:2)
Insert 2 large-bore cannulae
FBC, UEC, G+H, LFT, coags
IVF – aggressive approach to volume
Same defibrillation energy levels should be used as non-pregnant patient
- Drugs – there should normally be no alteration in algorithm drugs or doses; give inotropes/vasopressors
- Disability – AVPU (alert, voice, pain, unresponsive)
- Delivery
If no response to CPR within 4mins and >20wks, for perimortem CS as delivery of fetus and placenta reduces O2 consumption and improves venous return and cardiac output
No benefit if <20wks
Do incision that has most rapid access
Blood products
ICU monitoring
Central line or arterial line for BP monitoring
Thromboprophylaxis
Document
Debrief

Goal of therapy is to correct hypoxia and treat hypovolaemia so ischaemic consequences are prevented in mother

Goal is maternal resus not fetal survival

Question 4

OASIS

Answer 4

OASIS: obstetric anal sphincter injury; 6% overall risk
External sphincter - voluntary control, pudendal nerve, striated muscle
Internal sphincter - involuntary control, smooth muscle

Pelvic floor muscles:

• Levator ani muscles/deep (medial to lateral): pubrectalis, pubococcygeaus, iliococcygeus
• Superficial: ischiocavernosus, bulbocavernosus, transverse perineal
• Muscles of perineal body: pubococcygeus, transverse perineal, bulbocavernosus
• What is cut in an episiotomy - vaginal mucosa, perineal skin, bulbocavernosus, transverse perineal (superficial and deep), perineal body

Classification:
1st = perineal skin and vaginal mucosa
3nd = perineal muscle, but not anal sphincter
3A: <50% of external anal sphincter
3B: >50% of external anal sphincter but not internal anal sphincter
3C: external and internal anal sphincter
4th: EAS + IAS + anorectal mucosa

Risk factors:

• Previous OASIS (repeat risk 3-5%)
• Primip
• LGA
• Shoulder dystocia
• Prolonged 2nd stage
• Precipitous birth
• Episiotomy (esp midline > inferolateral)
• OP presentation
• AMA
• Instrumental delivery
• VBAC
• FGM

Prevention:

• Perineal massage
• Warm compression - during and between contractions in 2nd stage
• Maternal birth position - increased in standing/squatting/lithotomy
• Training of healthcare providers
• Episiotomy - controversial but protective in instrumental deliveries
• Perineal protection - left hand slowing delivery of head, right hand protecting perineum, mother not pushing when head is crowning, consider episiotomy

Presentation:

• Immediate
• Postpartum - with infection or unrecognised injury
• Delayed - after postpartum, usually present with loss of bowel control or faecal urgency

Repair:

• Overlap and end to end repair for EAS - no evidence for one over the other, surgeon’s choice
• Interrupted or mattress for IAS - no overlap
• Continuous or interrupted for anorectal mucosa
• Avoid tight sutures or figure of 8 as they can be haemostatic and cause tissue ischaemia

Management:

• Correct repair of tear in OT
• Antibiotics
• Analgesia, avoid opioids
• Ice pack
• Stool softeners
• Increase fibre and fluid in diet
• PFE
• Endoanal US
• Review 6-12 months postpartum
• Refer to gynaecologist or colorectal surgeon if experiencing incontinence
• 60-80% asymptomatic at 12months

Complications:

• Wound separation/breakdown - early repair of breakdown desirable to minimise short and long term perineal pain
• Pain
• Haematoma
• Infection
• Discharge
• Bleeding
• Fistula
• Faecal incontinence
• Dyspareunia
• Urinary incontinence
• prolapse
• Necrotising fasciitis - rare
• MOD for future pregnancies - offer CS if symptomatic or 2 or more OASIS or abnormal endoanal US
• If normal endoanal ultrasound and asymptomatic, discuss there is a risk of repeat OASIS tear (5-7%) and increased risk of faecal incontinence (17% if incontinent longer than 3 months post delivery)
• No evidence that prophylactic episiotomy in subsequent delivery would prevent OASIS hence decision for episiotomy should be clinical

Resources:

• Uptodate
• Greentop

Question 5

OASIS questions

Answer 5

Jan 2019

5. OASIS - difference between 3B and 3C, how to identify internal sphincter, difference between external and internal sphincters and their physiological roles

a. Explain the classification of obstetric perineal injuries. (5 marks) What is the difference between 3B and 3C?
- Classification by Sultan
- 3A: <50% of external anal sphincter
- 3B: >50% of external anal sphincter but not internal anal sphincter
- 3C: external and internal anal sphincter

b. How to identify internal sphincter
- Smooth muscle
- Deep to external sphincter
- Pale pink

c. What is the difference between external and internal anal sphincters What is the difference in their physiological roles (You may use a table).

EAS	IAS
Voluntary control	Involuntary control
Striated muscle	Smooth muscle
Pudendal nerve	
	Essential for resting continence
When damaged, causes faecal incontinence	When damaged, causes faecal incontinence and leakage

July 2012 Question 2

a. Explain the classification of obstetric perineal injuries. (5 marks)
- Based on Sultan’s classification
- First = perineal skin and vaginal mucosa
- Second = perineal muscle, but not anal sphincter
- 3A: <50% of external anal sphincter
- 3B: >50% of external anal sphincter but not internal anal sphincter
- 3C: external and internal anal sphincter
- 4th: EAS + IAS + anorectal mucosa

You are asked to review a primiparous woman in the labour ward who has just delivered and
sustained an extensive anal sphincter tear which extends into the anal canal.
b. Outline the surgical principles (4 marks) and choice of suture material (2 marks) you would
use.
- Inspect in birth unit
- Explain that this is a fourth degree tear that requires repair in operating theatre with good lighting, analgesia, sterile procedure
- Call senior obstetrician for assistance
- Need to repair in layers
- If bleeding, more urgent repair
- Lithotomy
- Start with anal mucosa – repaired in interrupted or continuous sutures with 3-0 vicryl inverted out of lumen
- Then internal anal sphincter – repair in interrupted or mattress sutures to approximate edges with 2-0 vicryl or 3-0 PDS
- Then external anal sphincter – can repair end to end or overlap (no evidence to support one over the other) with 3-0 PDS or 2-0 vicryl sutures
- Then repair perineal muscle by anchoring apex and doing continuous sutures to hymen and continuous sutures in perineal muscle – consider simple interrupted for better bulk
- Then perineal skin with 2-0 or 3-0 vicryl with subcutaneous sutures
- Bury superficial knots beneath perineal muscle to prevent irritation to skin
- Avoid figure of 8 as it can cause tissue ischaemia
- PR exam at the end of procedure to ensure no sutures through rectal mucosa
- IV broad spectrum antibiotics – minimum STAT dose, consider for 24 hours
- Avoid opiates
- Recommend laxatives
- Pelvic floor exercises
- Document, debrief, incident report
- Review in 6-12 weeks in clinic
- Endoanal ultrasound in 3 months

b. What advice would you give regarding subsequent pregnancies? Justify this advice. (4 marks)
- Mode of delivery in next pregnancy would depend on a few factors
- Ask whether she is planning for more children
- Needs endoanal ultrasound
- Reassure 60-80% of women are asymptomatic at 12months after delivery
- If she becomes symptomatic of faecal incontinence or flatal incontinence, to consider offering elective caesarean section for next delivery
- If there is a large defect in repair or abnormal endoanal ultrasound, consider offering elective caesarean section – unknown the significance of small defects
- If normal endoanal ultrasound and asymptomatic, discuss there is a risk of repeat OASIS tear (5-7%) and increased risk of faecal incontinence (17% if incontinent longer than 3 months post delivery)
- No role for prophylactic episiotomy – only perform episiotomy if clinical indicated
- Protect perineum at crowning
- Warm compression during second stage
- Need to be counselled about risks and benefits of both before making decision

Feb 2013 Question 11
- Same as July 2012

Question 6

Instrumental delivery

Answer 6

Indications:

• Maternal exhaustion
• Maternal medical conditions e.g. maternal cardiac or neuro disease so need to avoid pushing in 2nd stage
• Prolonged 2nd stage
• Fetal compromise

Prolonged 2nd stage:

• Recommend 3hrs pushing for nullip and 2hrs pushing for multip
• Can give longer with epidural

Contraindications for both:

• Extreme prematurity
• Fetal condition (e.g. osteogenesis imperfecta, fetal bleeding disorders)
• Unengaged head
• Unknown fetal positive
• Brow or face presentation
• Suspected CPD

Contraindications for vacuum:
ABSOLUTE
- <34wks - risk of IVH
- Fetal bleeding disorders (e.g. alloimmune thrombocytopaenia) or predisposition to fractures (e.g. osteogenesis imperfecta)
RELATIVE
- 34-36wks

Classification:

• Outlet - scalp visible on introitus without separating labia
• Low - head >2cm beyond spines but not on pelvic floor
• Midcavity - head engaged but leading point <2cm beyond ischial spines

Prerequisites:

• Fully dilated
• Membranes ruptured
• Head engaged
• Know fetal position, station, presentation, any asynclitism
• Patient consents
• Option for CS if needed
• Adequate analgesia
• Not too LGA or SGA
• Empty bladder - or fetal descent and reduce injury to bladder

How to minimise instrumental:
Antenatal
- Education about normal labour process
- Presenting in active labour rather than latent phase
Intrapartum
- Continuous support in labour
- Upright or lateral position in labour if not having epidural
- In 2nd stage with epidural, lateral position rather than upright as this increases rate of SVB
- If using epidural, not to reduce dose during pushing as this increases pain
- Delay pushing for 1-2hrs if nulliparous with epidural

Steps:

• Adequate analgesia
• Can confirm position with US
• Choice of vacuum (easier extraction, good maternal effort, less analgesia) vs forceps (higher success rate, unlikely to detach, can be used on preterm)
• For vacuum - determine flexion point -> place cup over point should be 6cm from anterior fontanelle and 3cm from posterior fontanelle-> check no maternal tissue trapped -> raise pressure to 100-150mmHg, exert force is 450-600mmHg -> dominant hand pulls and non-dominant hand puts counter pressure to prevent cup detachment -> keep stem perpendicular to plane of cup -> traction applied along axis of pelvis
• Mediolateral episiotomy - based on clinical judgement, most effective if primip or forceps
• Single STAT dose of IV augmentin to prevent endometritis within 6hrs of delivery (ANODE trial)

When to abandon:

• If unable to apply instrument
• If no descent with appropriate application and traction
• After 3 pulls and no imminent delivery - reconsider after 2 pulls and no descent
• After 2 pop offs
• Approx 15-20mins
• Fetus not delivered within a reasonable time

Complications: midpelvic operative delivery > 2nd stage caesarean delivery
MOTHER
- OASIS tears
- PPH
- Haematomas
- Pelvic floor damage
- Urinary retention
- Psychological distress
FETUS
- Subgaleal (vacuum)
- IVH
- ICH (multiple instruments)
- Fetal scalp abrasions
- Cephalohaematoma (vacuum)
- Retinal haemorrhage (vacuum)
- Shoulder dystocia
- Skull fracture
- Brachial plexus injury
- Facial nerve injury (forceps)
- External ocular trauma (forceps)
- Cervical spine injury (rotational forceps)
- Jaundice

No significant difference between instruments in risk of any neonatal injury, low APGAR <7 at 5mins or low pH in artery at birth

Forceps more likely to:

• Be successful
• More prolapse or OASIS injury
• More urinary incontinence
• More PPH
• Less cephalohaematoma, fetal retinal haemorrhage, jaundice or shoulder dystocia

Caesarean section after failed instrumental:

• More PPH
• Bladder injuries
• Fetal morbidity - ICH, need for resus, acidosis
• ICU admission

Rotational forceps:

• Risk of ICH and cervical spine injury
• Head must be engaged based on abdominal and VE
• Adequate analgesia
• Adequate experience or supervision
• Attempt rotation between contractions
• Low threshold to abandon procedure for CS

Post delivery care:

• Analgesia
• Voiding function - IDC for 12hrs post instrumental if spinal or epidural used (RCOG)
• VTE prophylaxis
• Pelvic floor rehabilitation
• Debrief delivery - counsel if OASIS; 80% will have spontaneous NVB in next delivery

Resources:

• Uptodate
• RANZCOG
• RCOG

Question 7

Instrumental questions

Answer 7

July 2019 - Instrumental vaginal delivery

A 28 year old P0 presents to you in antenatal clinic. She has had a low risk pregnancy and is now 20 weeks gestation, with no antenatal issues and BMI 30.

a) What are the antenatal and intrapartum evidence based ways she can minimise her chance of instrumental delivery in labour (3 marks)
- Antenatal
o Education about normal labour process
o Presenting in active labour rather than latent phase
- Intrapartum
o Continuous support in labour
o Upright or lateral position in labour if not having epidural
o In 2nd stage with epidural, lateral position rather than upright as this increases rate of SVB
o If using epidural, not to reduce dose during pushing as this increases pain
o Delay pushing for 1-2hrs if nulliparous with epidural

b) The Cochrane review “Instruments for assisted vaginal delivery”, discusses the benefits and risks of forceps and vacuum delivery. It is known that forceps are associated with greater degrees of maternal trauma but less risk of failure compared to vacuum. Outline the specific risks of forceps compared to vacuum and for each the relative risk associated with it (3 marks)
- Maternal
o Increased risk of OASIS tears – RR 1.89
o Increased risk of PPH – RR 1.71
o Increased risk of prolapse and pelvic floor dysfunction
o Increased risk of urinary incontinence – RR 1.77
- Fetal
o Increased risk of facial nerve palsy
o Increased risk of cervical spine fracture (rotational forceps)
o Reduced risk of retinal haemorrhage (RR 0.6), subgaleal haemorrhage or cephalohaematoma (RR 0.64)
o Reduced risk of neonatal jaundice (RR 0.79)

c) The risk of shoulder dystocia has a trend toward fewer cases of shoulder dystocia (RR 0.4, 95% CI 0.16-1.04) with vacuum delivery. Explain the above result and advise of its significance (2marks)
- The risk of shoulder dystocia is increased with LGA babies and CPD
- A vacuum would not be successful in these cases, and a forceps may be successful, therefore the cases of shoulder dystocia are less
- Not a significant difference as the confidence interval includes 1

She now presents in spontaneous labour.

d) She requires an instrumental delivery for failure to progress and has no regional analgesia. You decide to perform a pudendal block.
o Outline the course of the pudendal nerve (2 marks)
- Arises from the sacral spinal cord S2-4
- Passes between piriformis and ischiococcygeous muscle
- Leaves pelvis through greater sciatic foramen, crosses posterior to sacrospinous ligament and re-enters pelvis through less sciatic foramen
- Goes through pudendal canal and divides into branches

o Outline how you perform a pudendal black and the steps you take to minimise complications. (4 marks)
- Have to know where pudendal nerve is – if not ask for senior assistance
- Explain procedure to woman prior to performing – benefits of analgesia, risk of not working
- Draw up lignocaine 1% 10mL syringe with 18 to 20 guage needle
- Lithotomy
- Clean vagina with chlorhexidine
- Use alternate hand for either side
- Put middle finger on maternal ischial spine and run needle between index and middle finger 1cm medial to this and advance 1cm into tissue – insert 7-10mL each side with long needle
- Use the rest to infiltrate the perineum
- Minimise complications by:
o Ensuring you only insert minimal amount of local anaesthetic to prevent local anaesthetic toxicity
o Withdraw needle first to ensure you are not in a vessel prior to administering anaesthetic to avoid haematoma
o Avoid infection by using sterile technique