A G3P2 with two prior lower segment cesarean sections requests a trial of labour after cesarean (TOLAC). She has no prior uterine rupture and her prior cesarean incision was a low transverse incision. Which is the most significant independent risk factor that would make TOLAC inadvisable in her current pregnancy?
- A Two prior cesarean sections (vs one) ✓
- B Estimated fetal weight > 4 kg on ultrasound
- C Gestational age > 40 weeks
- D Prior postpartum haemorrhage at cesarean
Explanation
The number of prior uterine incisions is the most significant risk factor for uterine rupture during TOLAC. Two prior low transverse cesarean sections increase the uterine rupture risk to approximately 0.9–1.8% (vs ~0.5–0.9% for one prior LSCS). ACOG acknowledges TOLAC after two prior cesareans as a reasonable option in specific settings (level II/III facilities), but most guidelines consider two prior cesarean sections a relative contraindication or require counselling about elevated rupture risk. Macrosomia (> 4 kg) is a relative concern but not independently higher risk than EFW of 3.9 kg. Post-dates does not independently contraindicate TOLAC. Prior PPH is not an independent TOLAC-specific risk factor.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.