Topic Overview

The most rare yet most serious risk of vaginal birth after caesarean (VBAC) is that the scar on the uterus may break open (rupture) during labour. Women who have a low transverse caesarean scar have a lower risk of rupturing than women who have a vertical incision scar. About 5 to 9 out of 1,000 women (0.5% to 0.9%) with a low transverse scar have a uterine rupture during a trial of labour.footnote 1

A woman's risk of uterine rupture increases with:

  • Each additional uterine surgical scar.
  • Any uterine scar that reaches above the lower, thinner part of the uterus, such as a vertical (classical) scar.
  • The use of medicine to start (induce) labour. Some doctors avoid the use of any medicine to start a VBAC trial of labour. Other doctors are comfortable with the careful use of certain medicines to start labour or strengthen labour, such as oxytocin.

It is likely that the women who have a rupture have other risk factors, which are things that make them more likely to have this complication.

Having had a vaginal delivery during another pregnancy lowers the risk of uterine rupture during VBAC. Women who have delivered vaginally and later had a caesarean delivery have about one-fourth the risk of women who have had a caesarean delivery but no vaginal delivery.footnote 1

In the rare event that a uterine scar ruptures, it can be dangerous to both the mother and her infant.

Depending on severity, a rupture can:

  • Be mild and harmless.
  • Often be repaired. If it is not repairable, the uterus is removed (hysterectomy).
  • Cause severe maternal bleeding and a decrease in oxygen to the baby.
  • Cause fetal brain damage or death.



  1. American College of Obstetricians and Gynecologists (2010). Vaginal birth after previous cesarean delivery. ACOG Practice Bulletin No. 115. Obstetrics and Gynecology, 116(2): 450–463.


ByHealthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology

Current as ofMay 22, 2015