If you had a cesarean for your first birth, the question of how to deliver next time has both medical and personal layers. ACOG Practice Bulletin 205 (2019) endorses trial of labor after cesarean (TOLAC) as a reasonable option for most people with one prior low-transverse cesarean and a current pregnancy without contraindications. The decision turns on candidate factors, hospital capability, and personal preference.
This post walks through who is a good candidate, what predicts success, where the numbers come from, and what the conversation with your provider should cover.
The basic numbers
Across high-quality cohort studies and meta-analyses, the average VBAC success rate among people who attempt TOLAC is 60 to 80 percent. A 2010 NIH consensus statement and ACOG 205 both cite roughly 74 percent overall success.
The risk of uterine rupture after one prior low-transverse cesarean is approximately 0.5 to 0.9 percent. Rupture is the rare but serious complication that drives the recommendation for delivery in a facility able to perform emergent cesarean.
For comparison, repeat cesarean has its own risk profile: surgical site infection, bleeding, adhesions affecting future surgeries, longer recovery, and increased risk of placenta accreta in subsequent pregnancies. Both paths carry tradeoffs; neither is risk-free.
Who is a candidate
ACOG 205 considers TOLAC appropriate for most people with:
- One previous low-transverse cesarean.
- A clinically adequate pelvis.
- No other uterine scars or prior rupture.
- No contraindication to vaginal birth (placenta previa, certain malpresentations, etc.).
- Delivery in a facility capable of immediate cesarean.
Two prior low-transverse cesareans is also reasonable for selected candidates with appropriate counseling. Classical or T-shaped incisions (typically used for very preterm births or other specific indications) are generally a contraindication because rupture risk is markedly higher.
If you do not know what type of incision you had, request the operative report from your prior delivery. The skin incision (vertical or horizontal) does not tell you the uterine incision.
What predicts success
Grobman et al. (Obstet Gynecol 2007) studied over 7,000 TOLAC attempts in the MFMU Network and built a multivariable prediction model. The strongest predictors of success:
- Prior vaginal birth. Anyone who has delivered vaginally — before or after the cesarean — has substantially higher VBAC success.
- Indication for the prior cesarean. A non-recurring indication (breech, fetal distress) is more favorable than a recurring one (arrest of dilation or descent).
- Spontaneous labor. Going into labor on your own predicts success better than induction.
- Maternal age. Younger age is favorable but the effect is modest.
- BMI. Higher BMI lowers success probability somewhat.
The original calculator output a percentage; people with predicted success above 60 to 70 percent are typically considered good TOLAC candidates, though absolute thresholds are personal and clinical.
The 2021 race-neutral update by the same group removed race and ethnicity from the model after multiple analyses showed those variables did not improve predictive accuracy and were associated with disparities in counseling. Most US institutions now use the updated calculator.
What lowers success
- Induction or augmentation, especially with prostaglandins. Prostaglandin induction is associated with higher rupture rates and is generally avoided in TOLAC. Mechanical methods (Foley balloon) and oxytocin alone are considered safer if induction is needed.
- Short interpregnancy interval, specifically under 18 months from prior cesarean to next delivery, is associated with somewhat higher rupture risk.
- Postdates pregnancy. TOLAC at 41 to 42 weeks has lower success and slightly higher rupture rates than earlier spontaneous labor.
- Estimated fetal weight 4,000 grams or more, particularly above 4,500 grams.
- Recurring indication for prior cesarean, especially failure to progress in active labor.
These are not absolute disqualifiers. They are inputs into a personalized conversation.
What the day of labor looks like
If you are attempting TOLAC, expect:
- Continuous fetal monitoring. External monitoring is standard; internal can be added if tracings are difficult.
- IV access. Even if you intend a low-intervention birth, an IV is placed in case of emergency.
- Anesthesia available. Anesthesia awareness and a 24/7 capacity for emergent cesarean are prerequisites for TOLAC.
- Normal labor support otherwise. Position changes, hydrotherapy between monitoring sessions, doulas, and other supports are compatible with TOLAC in most centers.
Signs of possible rupture include sudden severe abdominal pain (especially between contractions), loss of fetal heart tones, abnormal fetal heart rate patterns, vaginal bleeding, and loss of labor progress. Continuous monitoring is what catches abnormal heart rate patterns early — the single most sensitive sign.
Repeat cesarean: the alternative
Elective repeat cesarean is the choice for many people, and it is a reasonable choice. Key points:
- ACOG recommends scheduling at 39 weeks 0 days for elective repeat cesarean unless an earlier delivery is medically indicated.
- Each subsequent cesarean increases risk of placenta accreta in future pregnancies, especially with three or more prior cesareans. This is one reason TOLAC is often discussed even for people who anticipate more children.
- Recovery after planned cesarean is typically 4 to 6 weeks. Recovery after vaginal birth is faster on average, but unplanned cesarean during a TOLAC attempt has the longest combined recovery.
How to think about the decision
A few framing questions worth sitting with:
- What is the indication for my prior cesarean, and is it likely to recur?
- Have I ever delivered vaginally?
- What is my predicted success on the MFMU calculator, and how does my provider counsel that?
- Does the hospital have 24-hour anesthesia and surgical staffing?
- How many more children might we have? More cesareans compound risk.
- How important is the experience of vaginal birth to me?
There is no single right answer. The 2010 NIH consensus statement explicitly framed both TOLAC and elective repeat cesarean as ethically and medically defensible options.
Where this fits in your prenatal timeline
VBAC counseling typically happens at the new-OB visit (8 to 12 weeks), revisited at 28 weeks, and finalized in late third trimester. You can use the Pregnancy Week Calculator to track milestones, and the Due Date Calculator for accurate dating, which matters because postdates pregnancy lowers TOLAC success.
If this is a twin pregnancy, the picture changes. See twin pregnancy due dates for the dating side; TOLAC for twins is possible in selected cases but requires careful candidate selection.
Questions to bring to the visit
- What was the type of uterine incision in my prior cesarean? Can I see the operative report?
- What is my predicted VBAC success?
- Does this hospital perform TOLAC, and what is the local success rate?
- What is the plan if I go past 40 weeks?
- What induction methods, if any, are used here for VBAC candidates?
The bottom line
VBAC is a reasonable choice for most people with one prior low-transverse cesarean and no other contraindications. Success averages 60 to 80 percent, predicted by prior vaginal birth, spontaneous labor, and the indication for the original cesarean. Uterine rupture risk is real but small (0.5 to 0.9 percent). The MFMU calculator gives a personalized success estimate, and the decision is ultimately a values-laden one made between you, your partner, and your provider.