Late Pregnancy · Birth Plan
VBAC Success Calculator
Will my VBAC work? Personalised success rate based on MFMU research. Plus what raises and lowers your chance, uterine rupture risk (~0.5% spontaneous labour), VBAC vs ERCS trade-offs, and how labour is monitored. NICE NG121 / RCOG.
Last reviewed 2 June 2026
VBAC success predictor (MFMU 2021)
Vaginal birth after caesarean — probability
y
Units
cm
kg
Enter age, height, and weight to compute the predicted VBAC success rate.
Based on the Grobman 2021 race-neutral MFMU calculator (Am J Obstet Gynecol 2021). The 2021 update removed race and ethnicity as predictors after the original 2007 model was found to systematically underpredict success in Black and Hispanic women, contributing to lower TOLAC offer rates. Uterine rupture risk in TOLAC is approximately 0.5-1 % across all candidates (ACOG PB 205).
What does this mean?
A successful VBAC means a vaginal delivery after a previous caesarean — it generally has the same recovery and risk profile as any vaginal birth (shorter hospital stay, less infection, easier subsequent pregnancies). The key trade-off is uterine rupture risk: ~0.5–1 % during TOLAC (trial of labour after caesarean) with one prior low-transverse incision (ACOG PB 205). Most experts recommend offering TOLAC if predicted success is ≥ 60–70 %, but it’s a personal decision in shared care with your obstetric team. Factors that raise success: any prior vaginal delivery (especially a prior VBAC — best predictor), spontaneous labour, lower BMI, younger age, non-recurring reason for the first caesarean. Things that lower it: two or more previous caesareans, prior arrest of labour, classical/T-incision uterus (TOLAC usually not offered), induction with prostaglandins (uterine-rupture risk rises with E2 + oxytocin).
What’s the difference between VBAC and TOLAC?
- TOLAC = Trial Of Labour After Caesarean (the attempt).
- VBAC = Vaginal Birth After Caesarean (a successful TOLAC).
- ~60-80% of TOLAC attempts succeed.
- Alternative: ERCS (Elective Repeat C-Section) — planned, no labour.
Am I a good candidate?
Favourable factors (success ~80%+):
- Previous vaginal birth (strongest predictor).
- Spontaneous labour.
- Previous C-section for NON-RECURRING reason (breech, fetal distress).
- BMI in normal range.
- Younger maternal age.
- Baby cephalic (head-down).
Unfavourable factors (success ~40-50%):
- Induction needed.
- High BMI.
- Gestational diabetes.
- Big baby (EFW >4 kg).
- Recurrent indication (e.g. previous failure to progress).
Risks of VBAC
Main risk: uterine rupture — previous scar tears.
- ~0.5% (1 in 200) spontaneous labour.
- ~1-1.5% with prostaglandin induction.
- Higher with classical scar (rare modern UK).
Can cause fetal distress, haemorrhage, baby/maternal injury, occasional death (~5% baby mortality if rupture).
Other risks: infection, transfusion, emergency C-section (~20-40% of TOLAC).
Benefits: faster recovery, easier future pregnancies, better breastfeeding start, family connection at birth.
Risks of ERCS (repeat C-section)
- Major abdominal surgery.
- Blood loss >1L (~5%), infection (~5%), anaesthesia complications.
- Slower recovery (6+ weeks vs 2-4 vaginal).
- Breastfeeding delay.
- Future pregnancy: placenta accreta risk rises with each C-section (~0.5% after 1, ~5% after 4).
- 30-day mortality ~3x higher than VBAC.
How VBAC labours are monitored
- Continuous CTG — fetal heart rate throughout.
- IV cannula for emergency access.
- Emergency C-section available within ~30 minutes.
- Water birth not generally offered (continuous CTG needed); some units have wireless / waterproof CTG.
- Epidural allowed — doesn’t increase rupture risk.
Can I be induced for VBAC?
- Spontaneous labour: lowest rupture risk (~0.5%).
- Prostaglandin induction: higher rupture (~1-1.5%); used cautiously.
- Mechanical induction (Foley balloon): lower rupture risk; preferred.
- Oxytocin augmentation: used cautiously, lower doses.
- Avoid misoprostol (Cytotec) — too risky for VBAC.
VBAC preparation
- Educate — “Birth After Caesarean” (Jenny Lesley), AIMS resources.
- Book consultant by 30 weeks to discuss plan.
- Birth plan: pool labour, mobility, pain relief preferences.
- Doula — evidence improves VBAC success.
- Hypnobirthing / mindfulness.
- Prenatal exercise for endurance.
- Aim for spontaneous labour — best success.
- Continuity of carer midwife model if available.
- Ask about unit’s VBAC success rate — varies.
If VBAC doesn’t work
Emergency or planned repeat C-section. Common reasons for switching: slow progress, fetal distress, rare rupture signs. Conversion ~20-40% of TOLAC.
Emotional aspect — disappointment normal; doesn’t mean “failed”. One complication-free labour sets stage for future success. Debrief birth with midwife is helpful.
Different scenarios — VBAC decisions
Scenario 1: Previous C-section for breech, now head-down baby
Highly favourable. Likely VBAC success ~80%+. Plan spontaneous labour, continuous CTG, supportive birth plan.
Scenario 2: Previous C-section for failure to progress at 7 cm
Less favourable but still ~50-65%. Consider VBAC. Smaller baby this time, different position can help. Discuss carefully.
Scenario 3: VBAC after 2 C-sections (VBA2C)
Possible — ~70% success in selected cases. Rupture rate slightly higher (~0.7-1.5%). Consultant review essential.
Scenario 4: Want VBAC but unit unsupportive
Options: second opinion within trust; supportive consultant; move care to another trust; AIMS support. Legal right to attempt VBAC if you choose.
Scenario 5: VBAC + GDM + big baby + induction needed
Lower success rate. Mechanical induction (Foley) safer than prostaglandins. Discuss honest risks vs benefits. Plan flexible.
Care guidance — planning VBAC
- Discuss with consultant by 30 weeks.
- Use MFMU calculator for personalised success estimate.
- Birth plan: pool early labour, mobility, intermittent positions.
- Aim for spontaneous labour — best outcomes.
- Continuous CTG in established labour.
- IV cannula + emergency C-section access.
- Avoid Cytotec if induction needed.
- Doula / continuity midwife improves success.
- Debrief regardless of outcome.
- Future pregnancies easier after successful VBAC.
Sources
- NICE NG121. Caesarean birth.
- RCOG Green-top Guideline 45. Birth after previous caesarean birth.
- ACOG Practice Bulletin 205. Vaginal birth after cesarean.
- Grobman WA, et al. MFMU Network VBAC calculator (updated 2021).
- AIMS (Association for Improvements in the Maternity Services). aims.org.uk.
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Frequently asked questions
What's the difference between VBAC and TOLAC?
TOLAC = Trial Of Labour After Caesarean (the ATTEMPT). VBAC = Vaginal Birth After Caesarean (a SUCCESSFUL TOLAC). About 60-80% of TOLAC attempts succeed. So 'planning VBAC' really means 'planning TOLAC and hoping for VBAC'. Alternative is ELECTIVE REPEAT C-SECTION (ERCS) — planned C-section without trying labour. This is one of the biggest birth decisions you'll make — your obstetric team will discuss likely success rate, risks, and your preferences in detail.
Am I a good candidate for VBAC?
FAVOURABLE FACTORS (higher chance of success ~80%+): (1) PREVIOUS VAGINAL BIRTH (before OR after C-section) — strongest predictor; (2) LABOUR started spontaneously; (3) C-section was for NON-RECURRING reason (e.g. breech, fetal distress) not 'failure to progress'; (4) BMI in normal range; (5) YOUNGER MATERNAL AGE; (6) BABY in CEPHALIC (head-down) position. UNFAVOURABLE FACTORS (lower success ~40-50%): induction needed, high BMI, gestational diabetes, big baby (EFW >4 kg), multiple previous C-sections, recurrent indication. The MFMU calculator (used here) gives personalised estimate.
What are the risks of VBAC?
Main risk: UTERINE RUPTURE — the previous scar tears. RARE: ~0.5% (1 in 200) for spontaneous labour; 1-1.5% with prostaglandin induction; higher with previous classical scar (rare in modern UK). UTERINE RUPTURE can cause: fetal distress, maternal haemorrhage, baby/maternal injury, occasional death (~5% baby mortality if rupture occurs). MONITORING: continuous CTG (fetal heart monitoring) in labour to catch early signs. OTHER risks: infection, blood transfusion, emergency C-section (~20-40% of TOLAC). BENEFITS: faster recovery, future pregnancies easier, possible better breastfeeding start, family connection at birth. SHARED DECISION.
What are the risks of repeat C-section (ERCS)?
MAJOR ABDOMINAL SURGERY. Risks: BLOOD LOSS (>1L in ~5%); INFECTION (~5%); ANAESTHESIA complications; SLOWER RECOVERY (6+ weeks vs 2-4 vaginal); MORE PAIN; BREASTFEEDING delay; FUTURE PREGNANCY complications increase with each C-section (placenta accreta — placenta growing into scar, can be life-threatening; ~0.5% with 1 prior, ~5% with 4 prior). 30-DAY MORTALITY ~3x higher than VBAC. BENEFITS: AVOIDS uterine rupture risk; PLANNED timing; PREDICTABLE; AVOIDS prolonged labour. RESPIRATORY ISSUES slightly higher in C-section babies (no labour 'squeeze'). NEITHER OPTION ZERO RISK.
What if my previous C-section was for failure to progress?
VBAC SUCCESS RATE LOWER (~50-65%) but NOT EXCLUDED. Factors matter: (1) PROGRESS REACHED — got to 7 cm before C-section better prognosis than 3 cm; (2) BABY SIZE this time vs last; (3) PELVIC DIMENSIONS — there's variability but pelvis doesn't change dramatically; (4) POSITION — back-to-back babies harder; (5) DURATION of previous labour. SOME women succeed because: this baby smaller, better position, more efficient labour. SHOULD STILL discuss VBAC with obstetric team — many women choose to attempt despite lower success rate.
How are VBAC labours monitored?
CONTINUOUS CTG — fetal heart rate monitored throughout. WHY: early signs of uterine rupture often fetal heart deceleration (BEFORE pain or bleeding). IV CANNULA in place — for emergency C-section access if needed. AVAILABILITY of emergency C-section within ~30 minutes. WATER BIRTH NOT generally offered (continuous CTG needed); some units have wireless / waterproof CTG. EPIDURAL allowed — doesn't increase rupture risk; can mask some symptoms (be alert to fetal heart changes). BIRTH POOL during early labour usually OK. PHYSIOLOGICAL THIRD STAGE possible.
Can I be induced for VBAC?
YES but with care. SPONTANEOUS labour = lowest rupture risk (~0.5%). PROSTAGLANDIN induction = HIGHER rupture risk (~1-1.5%) — used cautiously; NICE NG121 supports if benefits outweigh risks. MECHANICAL induction (Foley balloon, Cook catheter) = LOWER rupture risk than prostaglandins; preferred when induction needed. OXYTOCIN augmentation = used cautiously, doses lower than primary induction. AMNIOTOMY (artificial waters break) often safer than chemical induction. AVOID misoprostol (Cytotec) — too risky for VBAC. DISCUSS individual approach if induction needed.
How do I prepare for VBAC?
(1) EDUCATE — read 'Birth After Caesarean' (Jenny Lesley), AIMS resources; watch positive birth stories. (2) DECIDE early in pregnancy — book consultant appointment by 30 weeks. (3) BIRTH PLAN clear — pool labour, mobility, intermittent positioning, pain relief preferences. (4) DOULA — supportive birth attendant; evidence improves VBAC success. (5) HYPNOBIRTHING / mindfulness — calmer = labour more efficient. (6) PRENATAL exercise — fitness helps endurance. (7) GO INTO LABOUR spontaneously — best success; avoid sweep until 41 weeks. (8) SUPPORTIVE midwife continuity ideal. (9) DISCUSS unit's VBAC success rate (varies).
What happens if VBAC doesn't work?
EMERGENCY OR PLANNED REPEAT C-SECTION depending on situation. Most common reasons for switching: SLOW PROGRESS in labour; FETAL DISTRESS on CTG; RUPTURE SIGNS (rare). Conversion to C-SECTION ~20-40% of TOLAC attempts. EMOTIONAL aspect — disappointment normal; doesn't mean 'failed'. Try again with next baby if family planning. ONE COMPLICATION-FREE LABOUR even without VBAC sets stage for future success. C-SECTION after labour: scar may be different position; affects future pregnancies. DEBRIEF birth with midwife is helpful.
Will my next pregnancy be safer with VBAC vs another C-section?
VBAC often EASIER for future pregnancies. EACH C-SECTION increases: placenta accreta risk; placenta previa; adhesions; scar dehiscence; difficulty inserting future C-sections. AFTER 1 VBAC: subsequent VBACs ~90% successful; recovery faster. AFTER 4+ C-SECTIONS: significant complication risk — many specialists recommend completion of family. PLANNING FAMILY SIZE matters in VBAC discussion — if wanting 3+ children, VBAC may be safer long-term.
Can I have VBAC after 2 C-sections?
POSSIBLE — VBA2C (VBAC after 2 C-sections) has 70% success rate in selected cases. SAFETY: rupture rate ~0.7-1.5% (slightly higher than VBA1C). MORE CAUTION needed: previous classical scar = ABSOLUTE contraindication; T-shaped or inverted T scar = relative contraindication; J-shaped scar = increased risk. CONSULTANT REVIEW essential. NHS / RCOG support VBA2C in selected women. AFTER 3+ C-sections: VBAC rarely recommended — risks higher; usually elective C-section. SPECIALIST CONSULTATION needed.
What about home VBAC?
CONTROVERSIAL. NHS / RCOG generally recommend AGAINST home VBAC — emergency C-section access in ~30 min not possible. RUPTURE risk small but consequences catastrophic without immediate surgical access. INDEPENDENT MIDWIFERY can support home VBAC if you choose (UK private; not NHS). EVIDENCE: home VBAC success rate similar to hospital ~70-80%; rupture rate similar but worse outcomes if it happens. INFORMED CHOICE — discuss with multiple healthcare providers; respect for autonomy but understand risks. RUPTURE CAN be life-threatening for baby and mother — proximity to OR matters.
Will I feel a uterine rupture?
SIGNS: (1) SUDDEN sharp constant abdominal pain (not contraction pain) — but EPIDURAL can mask; (2) FETAL HEART RATE deceleration (CTG); (3) VAGINAL BLEEDING; (4) LOSS of fetal station (baby moves back up); (5) HEMODYNAMIC instability — drop in BP, rising HR; (6) SHOULDER TIP PAIN (blood irritating diaphragm); (7) Sudden CESSATION of labour pains. CONTINUOUS CTG often detects FIRST sign. IMMEDIATE C-section if suspected. RUPTURE is rare but team is vigilant — that's why monitoring is intensive in TOLAC labour.
Does breastfeeding go better with VBAC?
OFTEN YES. VBAC: spontaneous labour hormones (oxytocin, prolactin) primed; immediate skin-to-skin easier; baby usually alert and ready to feed; less morphine post-op; no abdominal pain interfering with positioning. C-SECTION: anaesthesia affects baby briefly; mum recovering from surgery; positioning awkward; pain meds; sometimes delay before holding baby. C-SECTION FEEDING POSSIBLE — but harder start. RUGBY HOLD often easier post-section. LACTATION CONSULTANT support useful either way. FED IS BEST — breast not always possible / preferred.
What if I really want VBAC but my hospital is unsupportive?
OPTIONS: (1) FORMAL second opinion within trust; (2) REQUEST consultant supportive of VBAC; (3) MOVE care to nearby trust with better VBAC support; (4) UK NHS: you have legal right to attempt VBAC if you choose; CAN'T be forced into C-section without consent; (5) ADVOCACY: AIMS (UK), birth doula support, lawyer in extreme cases. (6) DOCUMENT decisions in birth plan and notes; (7) FORMAL COMPLAINT if pressured. KEY: informed choice respected. Sometimes 'unsupportive' just means risk-averse; understand WHY — could be genuine clinical concern.
How does this relate to other calculators on BumpBites?
Companion: /calculators/bishop-score for cervix readiness; /calculators/induction (if added); /calculators/birth-plan-builder; /calculators/membrane-sweep; /calculators/contraction-timer; /calculators/hospital-bag-checklist; /calculators/labor-pain-coping; /calculators/breastfeeding-latch for postpartum.