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 decision must be weighed, individualised, and justified for the woman in front of you rather than reduced to 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, non-reassuring fetal status, 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
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).