Clinical overview
The caesarean section rate in South Africa is high and rising — well above the WHO's notional "population optimum" of 10–15%, and in many private and some public facilities it exceeds 40%. A consequence is that an ever-growing share of the antenatal population arrives with one or more uterine scars. Each of these women must, at some point in the third trimester, be counselled toward one of two mutually exclusive plans: planned VBAC (a trial of labour after caesarean, TOLAC, that succeeds in a vaginal birth after caesarean) or elective repeat caesarean section (ERCS). There is no third, risk-free option — the decision is a trade-off between competing harms, and the registrar's task is to lay those harms out honestly and help the woman choose.
VBAC matters because it is, for the appropriately selected woman, the safer and more durable choice: it avoids the cumulative surgical morbidity of repeat laparotomy — adhesions, bladder injury, and above all the steeply rising risk of placenta praevia and placenta accreta spectrum with each successive scar — and it sets her up for uncomplicated future pregnancies. Against this sits the signature catastrophe of TOLAC: uterine rupture, an obstetric emergency that can kill the fetus within minutes and exsanguinate the mother. Because the downside is sudden and severe, planned VBAC is fundamentally a question of where it is conducted as much as whether — it belongs in a unit with continuous fetal monitoring, immediate theatre access, and blood on hand. In the South African system that has explicit implications for level of care and for the counselling of women who book late or live far from a facility. The objective here is a "HOTS" discussion objective: you are expected to weigh, individualise, and justify — not merely recite a checklist. See also uterine-rupture, complicated-labour, and safe-caesarean-technique.
Core knowledge
Definitions
- TOLAC / trial of labour after caesarean — the intention to labour with a view to vaginal birth in a woman with a previous caesarean.
- VBAC — the outcome: a vaginal birth actually achieved after a previous caesarean. A failed TOLAC ends in an intrapartum (emergency) repeat caesarean.
- ERCS — elective repeat caesarean, planned and performed before labour (classically scheduled from around 39 weeks to minimise iatrogenic respiratory morbidity in the neonate — standard teaching).
Success rates
Across large series the overall planned-VBAC success rate is roughly 70–75% (RCOG GTG 45). The single strongest predictor is a previous successful vaginal birth — particularly a previous successful VBAC — which lifts success toward 85–90%. The strongest negative predictor is the indication that led to the first caesarean: a non-recurring indication (breech, fetal distress, placenta praevia) carries a better prognosis than a recurring one such as labour dystocia / cephalopelvic disproportion. Other factors that lower the probability of success include induced labour, no previous vaginal birth, maternal obesity, advanced maternal age, short inter-delivery interval, gestation beyond 41 weeks, and a large estimated fetal weight. Validated VBAC prediction calculators exist and can inform counselling, but they are aids to the conversation, not arbiters of it.
The central risk: uterine rupture
The headline figure to commit to memory is that planned VBAC after a single previous lower-segment transverse caesarean carries a uterine rupture risk of approximately 0.5% — about 1 in 200 (RCOG GTG 45). This is the number on which the whole discussion pivots. Around three-quarters of these ruptures occur in labour. When rupture occurs, the additional risk of delivery-related perinatal death is of the order of 1 in 1,000 planned VBACs — low in absolute terms but devastating when it happens, and broadly comparable to the background intrapartum risk faced by a nulliparous woman labouring for the first time. By contrast, the rupture risk with ERCS is very low (well under 0.02%).
Risk is modified by the scar and by intervention:
- Two previous caesareans — rupture risk is higher (figures of around 0.9–1.8% are quoted); VBAC may still be offered after careful individualised counselling, but the threshold for caution is higher.
- Previous classical (vertical upper-segment) scar — a contraindication to planned VBAC; rupture risk is high and can occur before labour.
- Induction and augmentation — both raise rupture risk above the spontaneous- labour baseline. Prostaglandins (and prostaglandin-then-oxytocin sequences) carry the highest induction-related rupture risk; oxytocin augmentation also raises risk in a dose-related way and must be used cautiously, by a senior, with continuous monitoring. Mechanical methods (transcervical balloon catheter) are generally preferred for cervical ripening in a scarred uterus, though the evidence base is limited (RCOG GTG 45 — flagged as evolving).
- Short inter-delivery interval (classically <12–18 months from previous caesarean) and single-layer unlocked closure of the previous hysterotomy are associated with higher rupture risk in observational data (standard teaching).
The competing harm: accreta spectrum
The argument for VBAC strengthens with every caesarean a woman is likely to have. The risk of placenta praevia, and of placenta accreta spectrum when a praevia overlies a scar, rises sharply with the number of previous caesareans — this is the long-game morbidity that ERCS quietly accumulates and that VBAC avoids (see antepartum-haemorrhage and postpartum-haemorrhage). A woman planning a large family has a particularly strong reason to consider VBAC now.
Assessment
Assessment of a woman for planned VBAC is a structured antenatal task, ideally completed and documented well before term, with a clear plan agreed and recorded.
History
- Number and type of previous caesareans — and crucially the type of uterine incision, which is not reliably inferred from the skin scar. Obtain the previous operation note wherever possible. A documented lower-segment transverse incision is the prerequisite for offering VBAC.
- Indication for the previous caesarean — recurring (dystocia/CPD) vs non-recurring (breech, distress, praevia).
- Any previous vaginal birth, and any previous VBAC — the dominant favourable predictor.
- Intra- and post-operative complications of the previous caesarean — extension/tear of the incision, sepsis, classical or inverted-T incision noted by the surgeon, all of which raise concern.
- Inter-delivery interval, parity, and the woman's plans for future pregnancies.
- Current pregnancy risk factors — placental site (exclude a low-lying placenta over the scar), fetal size, multiple pregnancy, malpresentation, and any new contraindication to labour.
Examination and investigations
- Routine antenatal assessment plus confirmation of gestational age (accurate dating underpins any plan to await spontaneous labour vs schedule ERCS) — see gestational-age-assessment.
- Ultrasound for placental localisation is essential: a placenta praevia or any suspicion of accreta over the scar mandates a planned caesarean and changes the entire pathway.
- Confirm presentation at term; a non-cephalic presentation alters the plan.
- There is no validated antenatal test that reliably predicts an individual scar's integrity. Routine sonographic measurement of lower-segment scar thickness is not recommended for clinical decision-making (RCOG GTG 45) — counsel on the population risk, not on a spurious individual measurement. Do not let an ultrasound number drive the decision.
- Standard booking bloods including haemoglobin and, in the SA context, HIV status with the woman established on antiretroviral therapy (TLD per the SA ART guidelines) — see hiv-in-pregnancy and hiv-counselling. HIV status per se is not a contraindication to VBAC; the mode-of-delivery decision follows viral load and standard obstetric indications, and a well-suppressed woman may labour normally.
Documenting the decision
The assessment culminates in a documented, shared decision: the woman's choice after balanced counselling, the agreed place of birth, the plan for spontaneous labour vs a backstop date for ERCS if she has not laboured (commonly discussed around 41 weeks, given that risk rises with prolonged pregnancy and that prostaglandin induction is best avoided), and the plan should she present in labour. This belongs in the antenatal record and is core to informed consent — see informed-consent.
Management
Counselling — the heart of a HOTS objective
Lay out the two pathways side by side, in absolute numbers, in language the woman understands. The comparison every registrar should be able to deliver fluently:
| Planned VBAC (TOLAC) | Elective repeat CS (ERCS) | |
|---|---|---|
| Success of plan | ~70–75% achieve vaginal birth | ~100% caesarean (planned) |
| Uterine rupture | ~0.5% (≈1 in 200) | very low (<0.02%) |
| Delivery-related perinatal death | ~1 in 1,000 | very low |
| Maternal future pregnancies | favours VBAC (avoids accreta accumulation) | rising praevia/accreta risk with each CS |
| Transient neonatal respiratory morbidity | lower | higher (esp. if pre-39 wk / not in labour) |
| Anaesthetic / surgical / VTE morbidity | confined to the ~25–30% who need intrapartum CS | applies to all |
Figures from RCOG GTG 45; absolute rates rounded for counselling.
Make explicit that a failed TOLAC (intrapartum emergency caesarean) carries more morbidity than a planned elective caesarean — so the woman is not choosing between "vaginal" and "elective CS" but between three possible end-states. Respect her autonomy: where there is no contraindication, the choice is genuinely hers, and a woman who declines VBAC is entitled to ERCS.
Figure J2.1 — Counselling trade-offs for planned VBAC/TOLAC, failed TOLAC, and elective repeat caesarean section.
Contraindications to planned VBAC
- Previous classical / inverted-T / J uterine incision.
- Previous uterine rupture.
- Any other standard contraindication to vaginal birth in the current pregnancy (e.g. placenta praevia, transverse lie).
- Two or more previous caesareans is a relative caution, not an absolute bar — individualise.
Conduct of labour — where SA level of care bites
Planned VBAC requires an environment that can convert to emergency caesarean immediately. In South African terms this means it should be conducted at a facility with 24-hour theatre, anaesthetic, and blood-bank access — in practice a district hospital with surgical capability, or a regional/tertiary unit, never at a midwife-obstetric unit (MOU) or clinic without on-site caesarean capability. A woman planning VBAC who books at a level without theatre must be referred for delivery; this is a recurring real-world counselling point in the SA setting where distances are large and late presentation common (NDoH National Integrated Maternal and Perinatal Care Guideline, NDoH, 2024). When she presents in labour:
- Confirm she is in established labour and review the agreed plan.
- Intravenous access, group-and-save / crossmatch, baseline bloods.
- Continuous electronic fetal monitoring (CTG) from the onset of established labour — an abnormal CTG is the commonest and earliest sign of uterine rupture (RCOG GTG 45; NICE NG235; NICE NG229). One-to-one care and a low threshold for senior involvement.
- Partogram with close attention to progress; poor progress in a scarred uterus warrants caution rather than enthusiastic augmentation — see partogram-use and complicated-labour.
- Oxytocin augmentation only on senior decision, titrated carefully, with continuous CTG; recognise it raises rupture risk.
- Avoid prostaglandin induction where possible; if induction is needed, a mechanical (balloon) method is generally preferred and the decision is a senior/consultant one (RCOG GTG 45).
- Epidural analgesia is not contraindicated — it does not mask rupture (breakthrough pain and the other signs persist) and can be a benefit.
Figure J2.2 — Green-light checklist for selecting a VBAC candidate and conducting labour in an appropriate facility.
The emergency: suspected uterine rupture — drill
Treat any of the warning signs below in a labouring woman with a scar as uterine rupture until proven otherwise. This is a "crash" situation. The drill:
- CALL FOR HELP — declare an emergency: senior obstetrician, anaesthetist, theatre team, paediatric/neonatal team, and alert the blood bank. Sound the maternal-emergency call.
- Resuscitate the mother — high-flow oxygen, left lateral tilt, two large- bore IV cannulae, rapid crystalloid, send urgent bloods (FBC, crossmatch, clotting), activate the massive transfusion protocol if shocked.
- Continuous fetal assessment — an acute fetal bradycardia or other acute, prolonged CTG abnormality is the most common presenting sign.
- IMMEDIATE delivery by laparotomy — the only definitive treatment is to deliver the baby and repair or remove the uterus. Move to theatre without delay; the decision-to-delivery interval is measured in minutes.
- At laparotomy: deliver the fetus, control haemorrhage, repair the rupture if feasible, or hysterectomy if repair is not possible or bleeding is uncontrolled.
- Anticipate massive obstetric haemorrhage — manage in parallel per the PPH / haemorrhage pathway (postpartum-haemorrhage, shock-management).
Warning signs of scar rupture: abnormal CTG (acute fetal bradycardia — the most common), new constant lower-abdominal/scar pain (may persist between contractions), cessation of previously efficient contractions, vaginal bleeding, haematuria, maternal tachycardia/hypotension/shock, loss of the presenting part on vaginal examination, and a change in abdominal contour.
Figure J2.3 — Emergency response to suspected uterine rupture during VBAC labour.
After delivery
Document the labour and outcome clearly. For the woman who achieves VBAC, record it prominently — a previous VBAC is the strongest favourable factor for any future attempt. Offer postpartum contraception and inter-pregnancy-interval advice before discharge (see postpartum-contraception); a longer interval reduces future rupture risk.
Red flags / pitfalls
- Do not infer the uterine incision from the skin scar. A Pfannenstiel skin incision can overlie a classical uterine incision. Get the operation note; if the uterine incision is unknown and cannot be established, counsel cautiously and lean toward the safer plan.
- Classical scar = do not labour. Missing a previous classical or inverted-T incision is a lethal error.
- Prostaglandin induction in a scarred uterus materially raises rupture risk — never a casual decision; prefer mechanical ripening, senior-led.
- Aggressive oxytocin augmentation of a scarred uterus that is failing to progress is a classic precipitant of rupture; poor progress is a reason to reassess, not to push harder.
- Conducting VBAC at a facility without immediate theatre and blood — in the SA context, failing to refer a VBAC candidate from a MOU/level-1 clinic to a unit with caesarean capability is a system failure that turns a 1-in-200 risk into a catastrophe. Place of birth is part of the plan.
- Treating the CTG complacently. An acute bradycardia in a VBAC is rupture until disproven — do not waste minutes on conservative measures.
- Relying on scar-thickness ultrasound to declare a scar "safe" — it is not validated for individual decision-making.
- Not having a documented, shared, dated plan for the woman who has not laboured by term — drifting past 41 weeks with no agreed backstop invites unplanned, higher-risk management.
- Over-counting caesareans the wrong way: remember the long game — each ERCS raises future praevia/accreta risk, so the "safe" repeat caesarean is not without its own escalating cost, especially in a woman wanting more children.
Evidence anchors
- RCOG Green-top Guideline No. 45 — Birth after Previous Caesarean Birth (VBAC). The primary source for this objective: success ~70–75%; single-LSCS rupture risk ~0.5% (1 in 200); ~1 in 1,000 delivery-related perinatal death; continuous CTG in labour; classical scar and previous rupture as contraindications; cautions on prostaglandin/oxytocin and on scar-thickness ultrasound.
- SA NDoH — National Integrated Maternal and Perinatal Care Guideline, 5th edition (2024). SA source of truth for level of care, referral pathways, and the requirement that planned VBAC occur where emergency caesarean and blood are immediately available.
- NICE NG235 — Intrapartum care (2023) and NICE NG229 — Fetal monitoring in labour (2022). Continuous CTG and continual risk assessment for the woman labouring with a uterine scar.
- Saving Mothers / NCCEMD (latest triennial report). Obstetric haemorrhage is a leading cause of maternal death in South Africa; uterine rupture and its haemorrhagic sequelae sit within this, reinforcing the place-of-birth and blood-availability imperatives.
- SA HIV/ART Consolidated Guidelines (2023; TLD first-line). HIV status does not contraindicate VBAC; mode of delivery follows viral load and obstetric indication.