What are the eligibility criteria for a trial of labor after cesarean (TOLAC)?

Eligibility Criteria for Trial of Labor After Cesarean (TOLAC)

TOLAC is appropriate for most women with one or two previous low transverse cesarean deliveries, provided they deliver in a facility capable of performing emergency cesarean within 30 minutes and have no absolute contraindications. 1, 2, 3

Absolute Contraindications

• Classical (vertical) uterine incision – This is an absolute contraindication to TOLAC regardless of other factors 1
• T-shaped uterine incision – Women with this incision type should not undergo TOLAC 4
• Previous uterine rupture – This represents an absolute contraindication 5

Eligible Candidates

• One or two prior low transverse cesarean deliveries – This is the standard eligibility criterion, with approximately 74% achieving successful vaginal birth 1, 2, 3
• Previous low vertical uterine incision – TOLAC can be offered after counseling, though evidence on risks and benefits is limited 5, 6
• Unknown uterine scar type – If the operative report is unavailable but circumstances suggest a low transverse incision was likely (e.g., term delivery, cephalic presentation), TOLAC can be offered after counseling 6

Facility Requirements

• Immediate surgical capability – The facility must be equipped to perform emergency cesarean delivery within 30 minutes of the decision to intervene 1
• Surgical response time for rupture – In cases of suspected uterine rupture, laparotomy should be initiated within 18 minutes to optimize maternal outcomes 1
• Available personnel – Obstetric, anesthetic, pediatric, and operating room staff must be readily available 6
• Written institutional policy – Each hospital should have clear protocols for physician notification and consultation for urgent cesarean 6

Clinical Factors That Support TOLAC (Not Contraindications)

• Previous vaginal delivery – This is the single strongest predictor of VBAC success and should lower the threshold for offering TOLAC 1, 2, 3
• Previous successful VBAC – Women with prior VBAC have even higher success rates in subsequent attempts 2, 3
• Multiple gestation – Twin pregnancy is not a contraindication to TOLAC 6
• Diabetes mellitus – This does not preclude TOLAC 6
• Suspected macrosomia – Estimated fetal weight ≥4,000g decreases success rates but is not an absolute contraindication 1, 2, 6
• Postdates pregnancy – Gestational age beyond 40 weeks does not contraindicate TOLAC 6

Relative Contraindications Requiring Individualized Counseling

• Inter-delivery interval <18 months – This significantly increases uterine rupture risk and warrants careful counseling 1, 6
• No previous vaginal delivery – Success rates are lower (though still ~60-70%), but TOLAC remains appropriate after discussion 1, 2
• Need for labor induction – Induction reduces VBAC success rates and increases rupture risk, particularly with prostaglandins; mechanical methods (Foley catheter) are preferred 1, 6

Intrapartum Management Requirements

• Continuous electronic fetal monitoring – This is mandatory throughout labor to detect signs of uterine rupture 6
• Intravenous access – Establish IV access before labor progresses 2, 3
• Neuraxial analgesia availability – Epidural or spinal anesthesia should be offered and does not increase rupture risk; early catheter placement facilitates rapid conversion to anesthesia if emergency cesarean becomes necessary 2, 3

Common Pitfalls to Avoid

• Excluding women with two prior cesareans – TOLAC is appropriate for women with two previous low transverse incisions, though rupture risk is modestly higher 6
• Denying TOLAC based on breech presentation or twins – These are not absolute contraindications, though management should be individualized 5, 6
• Overreliance on predictive models – Scoring systems have limited clinical utility in determining TOLAC candidacy 2, 3
• Failing to document scar type – The previous operative report should be obtained; if unavailable, delivery circumstances help estimate incision type 6