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 out of 1,000 women (0.5%) 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.

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.