Clinical Scenario: 30-year-old G2P1L1 with One Previous Lower Segment Caesarean Section at 39 Weeks Wanting Vaginal Delivery

1. Selection Criteria for Vaginal Birth After Caesarean (VBAC)

Favourable Criteria (Women Likely to Succeed)

• Only one previous caesarean delivery with a low transverse uterine incision (the scar at the lower uterine segment, horizontal - this is the safest scar for a trial of labour)
• No previous classical (vertical, fundal) uterine incision
• No previous extensive transfundal uterine surgery (e.g., myomectomy involving the fundus)
• Previous caesarean was NOT performed for cephalopelvic disproportion (CPD) or failure to progress in active labour - because these conditions may recur
• A prior successful vaginal delivery (before or after the caesarean) is the strongest positive predictor of VBAC success

• Adequate pelvis (clinically assessed - no obvious bony pelvic contraction)
• No other uterine scars or anomalies in the current pregnancy
• Singleton pregnancy
• Cephalic (head-down) presentation
• Estimated fetal weight below 4000 grams (macrosomia increases risk)
• Spontaneous onset of labour is more favourable than induced labour
• Maternal age below 40 years
• No placenta praevia, placenta accreta, or malpresentation

• Immediate availability of a physician capable of performing an emergency caesarean section
• Immediate availability of anaesthesia (general and/or regional) to support an emergency caesarean
• Availability of blood bank and transfusion services
• Neonatal intensive care unit support available

Predictors of Successful VBAC (Summary)

1. Are younger than 40 years old
2. Have had only one prior caesarean
3. Have a prior caesarean that was NOT for failure to progress or cephalopelvic disproportion
4. Go into spontaneous labour
5. Have a baby weighing 4000 grams or less
6. Have had a prior successful vaginal delivery

2. Intrapartum Management During Trial of Labour After Caesarean (TOLAC)

Admission and Monitoring

• Admit to a hospital with immediate surgical and anaesthetic facilities - trial of labour should NOT be conducted in a low-resource or isolated setting
• Continuous electronic fetal heart rate monitoring throughout labour - this is mandatory, not optional
• Intravenous access must be secured at the time of admission
• Blood grouping and cross-matching should be done and blood should be kept ready
• Baseline vital signs, uterine palpation, and assessment of scar site tenderness

Labour Progress

• Allow labour to progress normally
• Oxytocin augmentation is not absolutely contraindicated but must be used cautiously and only with careful monitoring - use the lowest effective dose
• An internal uterine pressure catheter is recommended when labour is being medically enhanced or induced, as it allows detection of loss of contraction intensity (an early sign of uterine dehiscence or rupture)
• Avoid prostaglandins (misoprostol, dinoprostone) for cervical ripening or induction - they are associated with a significantly increased risk of uterine rupture in women with a scarred uterus

Anaesthesia

• Epidural analgesia is permitted and is NOT contraindicated - this is a common misconception. Epidural analgesia does not mask the pain of uterine rupture sufficiently to prevent diagnosis
• Epidural may actually be beneficial - it reduces maternal distress and allows rapid conversion to operative anaesthesia if emergency caesarean becomes necessary

Surveillance for Uterine Rupture

• Fetal heart rate decelerations and fetal distress - the most common and earliest sign
• Heavy vaginal bleeding
• Decreasing station or complete loss of the presenting part (the fetal head retracts back up into the abdomen)
• Loss of contraction intensity as measured by internal uterine pressure catheter
• Uterine or pelvic pain in between contractions (not just during them)
• Maternal haemodynamic instability (tachycardia, hypotension) suggesting haemoperitoneum
• Bloody urine (may suggest bladder injury)

Preparation for Emergency

• A written informed consent must be documented prior to commencing trial of labour
• The operating theatre should be placed on standby
• Paediatric (neonatal) team should be informed and available
• Decision-to-delivery interval for emergency caesarean should ideally be under 30 minutes

3. Contraindications to VBAC

Absolute Contraindications

1. Previous classical (vertical) caesarean section - the fundal scar ruptures at a much higher rate (up to 12%) and can rupture silently before labour even begins
2. Previous extensive transfundal uterine surgery (e.g., full-thickness myomectomy involving the fundus or cornual region)
3. Two or more previous uterine scars - insufficient safety data; risk of rupture is higher
4. Previous uterine rupture (the scar is weak and unreliable)
5. Previous inverted T-incision or J-incision (extensions from a low transverse incision into the fundus)
6. Contracted or inadequate pelvis (confirmed cephalopelvic disproportion from current or prior assessment)
7. Any situation where vaginal delivery itself is contraindicated - placenta praevia, vasa praevia, transverse lie, cord prolapse

Relative Contraindications / Situations Requiring Caution

• Estimated fetal weight above 4000 grams (macrosomia)
• Previous caesarean for failure to progress or cephalopelvic disproportion (risk of recurrence)
• Absence of a prior successful vaginal delivery
• Multiple gestation (twins)
• Breech presentation
• Postterm pregnancy
• Institution without 24-hour surgical and anaesthetic support

4. Complications of Trial of Labour After Caesarean (TOLAC)

Maternal Complications

1. Uterine rupture - the feared complication, occurring in approximately 0.5% to 0.9% of women with a low-transverse scar undergoing a trial of labour. Risk is higher with:
   • Classical or vertical scar
   • Use of prostaglandins
   • Induced (versus spontaneous) labour
   • Short inter-delivery interval (less than 18-24 months between the previous caesarean and current delivery)
2. Uterine dehiscence - a partial or incomplete separation of the scar without full rupture into the peritoneal cavity; may be silent and found incidentally at caesarean or postoperatively
3. Haemorrhage - from uterine rupture, placenta accreta (higher incidence with scarred uterus), or operative delivery
4. Hysterectomy - emergency peripartum hysterectomy may be required to control bleeding from uterine rupture; rates are higher with failed VBAC followed by emergency caesarean
5. Bladder and bowel injury - during emergency caesarean in the context of dense adhesions from prior surgery

• Wound infection (if emergency or repeat caesarean becomes necessary)
• Thromboembolic events
• Prolonged hospital stay
• Blood transfusion
• Failed trial of labour necessitating emergency caesarean - this carries higher morbidity than an elective repeat caesarean performed under controlled conditions

Fetal and Neonatal Complications

1. Fetal hypoxia and acidosis - due to sudden uterine rupture compromising uteroplacental circulation
2. Perinatal asphyxia - if uterine rupture is not recognised and delivery expedited immediately
3. Hypoxic Ischaemic Encephalopathy (HIE) - permanent neurological damage in the neonate
4. Perinatal death - fetal death rates are higher with uterine rupture; immediate delivery within minutes is required to prevent death
5. Fetal expulsion into the peritoneal cavity - in complete uterine rupture, the fetus and placenta may be extruded into the mother's abdomen, requiring immediate laparotomy

Summary for this Patient (G2P1L1 with One Previous Lower Segment Caesarean Section, 39 Weeks)

• The pelvis is assessed as adequate
• The previous caesarean was not for cephalopelvic disproportion or failure to progress
• There are no other uterine scars
• Fetal weight is estimated at below 4000 grams
• The institution has 24-hour surgical and anaesthetic capacity

• Management of Premature Rupture of Membranes
• External Cephalic Version
• Partograph
• Intrauterine Growth Restriction

• Bishop Score
• Brow Presentation
• Assisted Breech Delivery
• Cervical Cerclage
• Causes of Intrauterine Fetal Death
• Retained Placenta
• Mechanism of Labour in Occipito-Anterior Position
• Physiology of Lactation
• Uterine Inversion
• Neonatal Resuscitation