Vaginal Birth After Caesarean (VBAC)
Summary
Vaginal Birth After Caesarean (VBAC) is a planned vaginal delivery for a woman who has had a previous Caesarean Section (usually a Lower Segment Caesarean Section - LSCS). The attempt at vaginal delivery is called Trial of Labour After Caesarean (TOLAC). VBAC is successful in approximately 72-76% of appropriately selected women, offering benefits of avoiding repeat major surgery and better outcomes for future pregnancies. The primary risk is Uterine Scar Rupture (~0.5%), which is a rare but potentially catastrophic complication with risk of fetal hypoxia and maternal haemorrhage. VBAC should be offered to eligible women with careful counselling, and labour should occur in a unit with access to immediate emergency Caesarean Section. [1,2]
Clinical Pearls
"Once a Section, Always a Section" is OUTDATED: The vast majority of women with one previous LSCS can safely attempt VBAC.
Rupture Risk ~0.5%: This is the key risk. It rises if the woman has had more than one CS, if induction with Prostaglandins is used, or if the uterine incision was classical (vertical).
Continuous CTG is Mandatory: Fetal heart rate abnormalities are often the first sign of scar dehiscence or rupture.
The Best Predictor of Success is Previous Vaginal Delivery: A woman who has previously delivered vaginally (before or after the CS) has an ~85-90% chance of successful VBAC.
Demographics
- CS Rate: ~25-30% of UK deliveries are by Caesarean Section.
- VBAC Rate: ~35-40% of eligible women attempt VBAC in the UK (varies by unit).
- Success Rate: ~72-76% overall. Higher if previous vaginal delivery (87%).
Factors Affecting Success
| Factor | Effect on Success |
|---|---|
| Previous Vaginal Delivery | Strongest positive predictor (~87% success). |
| Previous CS for Non-Recurrent Indication | (e.g., Breech, Fetal distress). Better than failure to progress. |
| Spontaneous Labour Onset | Higher success than induced labour. |
| BMI less than 30 | Higher success. |
| Adequate Birth Weight (less than 4kg) | Higher success. |
| Short Inter-Delivery Interval (less than 18 months) | Slightly lower success, higher rupture risk. |
Absolute Contraindications to TOLAC
| Contraindication | Rationale |
|---|---|
| Previous Classical (Vertical/Upper Segment) CS Incision | Very high rupture risk (4-9%). Elective CS mandatory. |
| Previous Uterine Rupture | Contraindicated. |
| Previous Fundal Uterine Surgery (e.g., Myomectomy entering cavity) | High rupture risk. |
| More than 2 Previous CS | Increased rupture risk. Generally recommend elective repeat CS (case-by-case). |
| Placenta Praevia | Requires elective CS regardless. |
Relative Cautions
- Need for induction of labour (especially with Prostaglandins).
- Short interpregnancy interval (less than 12-18 months).
- Suspected macrosomia (>4kg).
- Maternal request for Elective Repeat Caesarean Section (ERCS).
Benefits of VBAC (vs Elective Repeat CS)
| Benefit | Notes |
|---|---|
| Avoids Major Abdominal Surgery | Shorter recovery. Less pain. |
| Lower Risk of Surgical Complications | Infection, Haemorrhage, Thromboembolic disease. |
| Better for Future Pregnancies | Avoids multiple repeat CS and associated complications (Placenta Accreta Spectrum). |
| Shorter Hospital Stay | ~24-48h vs 48-72h. |
| Improved Breastfeeding Initiation | Some evidence. |
Risks of VBAC (vs Elective Repeat CS)
| Risk | Incidence | Notes |
|---|---|---|
| Uterine Scar Rupture | ~0.5% (1 in 200) | The primary concern. Can cause fetal death or HIE, maternal haemorrhage, hysterectomy. |
| Emergency Caesarean Section | ~25% | If TOLAC fails (non-progressive labour, CTG concern). Carries higher morbidity than elective CS. |
| Neonatal HIE | ~0.08% VBAC vs ~0.01% ERCS | Small increased risk due to rupture risk. |
| Perineal Trauma | As per any vaginal delivery | 3rd/4th degree tears possible. |
| Failed TOLAC | ~25% | Woman then has an emergency CS, with higher complication rate than planned ERCS. |
Signs of Scar Rupture (Emergency)
- Fetal Bradycardia / Pathological CTG: Often the FIRST sign. Sustained drop in fetal heart rate.
- Sudden Severe Abdominal Pain: (May be described as "tearing" pain, or different from contractions).
- Vaginal Bleeding: (May be minimal initially).
- Cessation of Contractions: (Uterus may feel "soft").
- Maternal Tachycardia / Hypotension (Shock).
- Easily Palpable Fetal Parts: (If rupture is complete and fetus extrudes into abdomen – late sign).
Management of Rupture
- Crash Caesarean Section (Category 1): Decision to delivery less than 15-30 minutes.
- Resuscitation: Maternal (fluids, blood), Neonatal (Paediatrician present).
- Surgical Repair or Hysterectomy: Depending on extent of rupture.
Antenatal
- Review Previous CS Notes: Confirm type of incision (Lower Segment?), Indication, Any complications.
- Ultrasound for Fetal Position/Weight: Standard antenatal assessment.
During TOLAC
- Continuous Electronic Fetal Monitoring (CTG): Mandatory throughout active labour. First sign of rupture is often CTG abnormality.
- IV Cannula in Situ: Ready for emergency.
Management Algorithm
WOMAN WITH 1 PREVIOUS LSCS
Requesting VBAC / Counselling
↓
CHECK ELIGIBILITY
(Type of previous incision? Any contraindications?)
┌────────────────┴────────────────┐
ELIGIBLE CONTRAINDICATED
(Lower Segment CS) (Classical CS, >2 CS, Rupture Hx)
↓ ↓
COUNSELLING ELECTIVE REPEAT CS (ERCS)
(Benefits vs Risks of VBAC)
↓
WOMAN'S CHOICE
┌────────────┴────────────┐
TOLAC (VBAC attempt) ERCS
↓
LABOUR ONSET
┌────────────┴────────────┐
SPONTANEOUS INDUCTION (If needed)
(Preferred) - Balloon Catheter preferred
↓ - Prostaglandins CAUTIOUS
ACTIVE LABOUR (↑ Rupture Risk)
↓ - Oxytocin can be used
CONTINUOUS CTG (Mandatory)
IV Access, In Hospital with Theatre
↓
PROGRESS?
┌────────────┴────────────┐
GOOD PROGRESS SLOW PROGRESS / CTG CONCERN
→ Vaginal Delivery → Emergency CS (Category 2-1)
↓
SUCCESSFUL VBAC!
(72-76% of attempts)
Intrapartum Management
| Item | Recommendation |
|---|---|
| Setting | Consultant-led unit with immediate access to emergency CS (Theatre staffed 24/7). |
| IV Cannula | In situ from active labour. |
| Fetal Monitoring | Continuous Electronic Fetal Monitoring (CTG). |
| Epidural | Permitted. Does not mask rupture signs (CTG is first sign). |
| Oxytocin Augmentation | Can be used if slow progress. Use cautiously. Slightly increases rupture risk. |
| Induction of Labour | Balloon catheter preferred (lower rupture risk than Prostaglandins). |
| Prostaglandins (PGE2) | Use with caution. Increases rupture risk (~2-3x). Misoprostol contraindicated for TOLAC. |
Of VBAC Attempt
| Complication | Notes |
|---|---|
| Uterine Scar Rupture | ~0.5%. Emergency. Requires immediate CS. |
| Failed TOLAC → Emergency CS | ~25%. Higher morbidity than elective CS. |
| Neonatal HIE / Death | Rare but increased vs ERCS (related to rupture). |
| Maternal Haemorrhage | If rupture or emergency CS. |
Of Elective Repeat CS (For Comparison)
- Surgical morbidity (bleeding, infection, organ injury - especially with multiple CS).
- Longer recovery.
- Increased risk of Placenta Accreta Spectrum in future pregnancies.
- VBAC Success Rate: 72-76% overall. 87% if previous vaginal delivery.
- Rupture Rate: 0.5% (1 in 200) with spontaneous labour. Higher with Prostaglandin induction.
- Maternal/Neonatal Deaths: Extremely rare with appropriate monitoring and rapid emergency CS capability.
- Repeat ERCS Outcomes: Good surgical outcomes in modern practice, but cumulative morbidity increases with each CS.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Green-Top Guideline No. 45 | RCOG | VBAC should be offered to eligible women. Continuous CTG. Prostaglandins cautiously. |
| ACOG Practice Bulletin | ACOG (USA) | TOLAC reasonable for most women with 1 prior low transverse CS. |
Landmark Evidence
- MFMU Network VBAC Study: Established predictors of success and rupture rates.
- NICHD Rupture Risk Data: Quantified rupture rates by induction method.
What is VBAC?
VBAC stands for Vaginal Birth After Caesarean. If you have had a Caesarean Section before, you may still be able to give birth vaginally next time. This attempt is called a "Trial of Labour."
How likely is it to work?
About 3 out of 4 women (72-76%) who try VBAC have a successful vaginal delivery. If you have had a vaginal birth before, your success rate is even higher (~87%).
What are the risks?
The main risk is that the scar from your previous Caesarean can open (rupture) during labour. This is rare (about 1 in 200 labours) but is serious. If this happens, we would need to do an emergency Caesarean Section immediately. That is why we continuously monitor your baby's heart rate throughout labour – it tells us if anything is wrong.
What are the benefits?
Avoiding another operation means a quicker recovery, less pain, and a shorter hospital stay. It is also better for future pregnancies.
What are my options?
You can choose to try for a VBAC (TOLAC) or you can choose an elective Repeat Caesarean Section. We will support your choice after discussing the risks and benefits for your individual situation.
Primary Sources
- Royal College of Obstetricians and Gynaecologists. Green-Top Guideline No. 45: Birth After Previous Caesarean Birth. 2015.
- American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 205: Vaginal Birth After Cesarean Delivery. 2019.
Common Exam Questions
- Success Rate: "What is the approximate success rate of VBAC?"
- Answer: ~72-76% (Higher if previous vaginal delivery).
- Main Risk: "What is the main risk of VBAC?"
- Answer: Uterine Scar Rupture (~0.5%).
- First Sign of Rupture: "What is often the first sign of uterine rupture?"
- Answer: Fetal Heart Rate Abnormality (Pathological CTG / Prolonged Bradycardia).
- Contraindication: "When is VBAC contraindicated?"
- Answer: Previous Classical (Vertical) Caesarean Section. Previous Uterine Rupture.
Viva Points
- Prostaglandins and Rupture Risk: Explain that Prostaglandin induction increases rupture risk (2-3x). Balloon catheter or Oxytocin are preferred if induction is needed.
- Predictors of Success: Previous vaginal delivery is the strongest positive predictor.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.