TOLAC delivers high VBAC success, but uterine rupture risk remains the defining trade-off
A large meta-analysis of women with one prior uterine scar places trial of labour after caesarean, or TOLAC, in a much sharper clinical frame. Across 32 studies and 1,287,757 women, the pooled vaginal birth after caesarean success rate reached 72.4%, a figure that makes spontaneous vaginal delivery a realistic outcome for most carefully selected patients rather than an exception. The same analysis also makes the central hazard plain: uterine rupture occurred more often with TOLAC than with elective repeat caesarean delivery, with a pooled rate of 0.47% versus 0.026% and an odds ratio of 7.21.
The numbers do not support a simplistic either-or rule. They support individual risk assessment at the bedside.
The review focused on studies published between January 2021 and March 2026, using pooled odds ratios, a random-effects model, and Newcastle–Ottawa Scale assessment of study quality. Heterogeneity was moderate to substantial for the main efficacy outcome, with I² at 63% for VBAC success, which is exactly what clinicians would expect in a real-world obstetric question shaped by labor management, prior cesarean indications, parity, and local thresholds for intervention. Even with that variability, the signal is consistent: most women attempting labor after one cesarean scar do deliver vaginally.
Maternal benefit extends beyond avoiding surgery
The maternal profile favors labor in several important domains. TOLAC was associated with lower odds of postpartum haemorrhage requiring transfusion, with an odds ratio of 0.68, and lower odds of wound infection, with an odds ratio of 0.52. Those findings reflect more than statistical convenience. Avoiding a second abdominal operation reduces incision-related infectious exposure and bypasses the surgical tissue disruption that can drive blood loss, postoperative pain, and delayed recovery. In practical obstetric terms, a successful vaginal birth after cesarean can mean less morbidity in the immediate postpartum period and less cumulative surgical burden across future pregnancies.
At the same time, rupture remains the event that reshapes counseling. Uterine rupture is uncommon, yet the difference between 0.47% and 0.026% is clinically consequential because the event can escalate rapidly into fetal distress, hemorrhage, emergency surgery, and maternal instability. The biologic vulnerability is straightforward: a prior scar creates a structural weak point that must withstand intense contractile force during labor. A scar that appears stable on paper can still fail under physiologic stress, which is why delivery planning around TOLAC cannot be reduced to a generic institutional policy.
Neonatal outcomes were similar when delivery occurred at term
Neonatal data in this analysis were reassuring in the subgroup delivered at 39 weeks or later. NICU admission rates were not significantly different between TOLAC and elective repeat caesarean delivery, with an odds ratio of 0.89 and a confidence interval crossing unity. That finding narrows the argument that repeat surgery automatically confers neonatal advantage once term delivery is achieved. It also suggests that much of the neonatal risk conversation may hinge less on the mode of delivery itself than on timing, labor course, and the need for urgent intervention when labor fails.
A term strategy matters because late-preterm and early-term delivery can distort neonatal comparisons. By restricting this outcome to pregnancies delivered at or beyond 39 weeks, the analysis reduced one major source of confounding. The result still did not show a clear neonatal penalty for TOLAC, which strengthens the case for shared decision-making rather than reflexive repeat surgery in every patient with one uterine scar.
Lower uterine segment thickness sharpened prediction
One of the more clinically usable findings involved lower uterine segment, or LUS, thickness. When LUS thickness measured at least 3.0 mm, VBAC success rose to 76.8% and rupture fell to 0.31%. This is the kind of information that changes a counseling conversation from abstract probabilities to personalized risk stratification. A thicker lower uterine segment is not a guarantee of safety, but it likely reflects a more robust scar interface and a better chance that the uterus can tolerate labor.
The physiologic logic is credible. Scar thickness is a surrogate for myometrial integrity, and a thicker segment may better resist the tensile forces generated during contractions and cervical change. In that sense, imaging does not replace clinical judgment; it refines it. A patient with a favorable LUS measurement and no other major obstetric contraindications sits in a different risk category from a patient with a thinner scar and additional factors that make emergency surgery more likely.
Institutional restriction looks harder to justify than individualized counseling
The pooled evidence does not support a blanket ban on TOLAC for all women with one previous cesarean. It supports structured counseling, readiness for emergency response, and selective use of scar assessment when available. A policy that treats every prior cesarean scar as equivalent ignores the wide spread in anatomy, prior indication, labor history, and current pregnancy features that influence the chance of success and the likelihood of rupture.
What matters at the bedside is not only the scar but the whole labor context: whether the previous cesarean was for a nonrecurrent indication, whether the current pregnancy is term, whether induction is planned, and whether immediate surgical capability exists. The meta-analysis cannot answer every operational question, but it does show that the default assumption should not be that repeat caesarean is always safer or always more effective. The data point in a more nuanced direction: many women can achieve VBAC, some will face rupture, and the balance shifts when imaging suggests a stronger lower uterine segment.
Counseling should center on absolute risk, not fear alone
For most patients, the counseling challenge lies in making a rare but serious complication feel proportionate rather than catastrophic. A rupture rate below 1% may sound small, yet it carries high stakes because the event can unfold quickly in labor. At the same time, repeat surgery is not benign. It brings its own hemorrhagic, infectious, anesthetic, and future-pregnancy costs, and those burdens accumulate across a reproductive lifetime.
The most useful message from this synthesis is not that TOLAC should be universal or restricted. It is that counseling should be individualized, with lower uterine segment thickness used as one additional piece of evidence when available. The analysis leaves open how best to standardize LUS measurement across settings, how induction protocols influence rupture risk in comparable populations, and which subgroups gain the most from a planned repeat operation. Those unanswered implementation questions will shape practice long after the pooled estimates themselves are absorbed into guidelines.