Trial of labor after caesarian (TOLAC) is the term for an attempted birth in a patient who has had a previous caesarean section. It may result in a successful VBAC (vaginal birth after caesarian) or a repeat caesarian section. In approximately 20-40% of TOLACs, a caesarian is performed. TOLAC is recommended when a patient has had one previous caesarian section using a low transverse uterine incision. The main risks of TOLAC are emergency caesarian section and uterine rupture.