Because the uterine scar for most caesarian sections is low on the uterus, women who undergo TOLAC (trial of labor after cesarean), are able to give birth vaginally 60–80% of the time. But if problems arise during TOLAC, the baby may need to be born by emergency cesarean delivery. Because uterine rupture can be sudden and unexpected labor outside of a hospital can delay delivery and increase the risk of injury and death for both mother and baby in an emergency. Some surgery for fibroids can result in a similar risk for uterine rupture. An unknown type of prior uterine scar is a contraindication for TOLAC so review of prior surgical records is essential part of the evaluation.
RISKS
Maternal risks
• Maternal hemorrhage
• Infection
• Thromboembolism
• Placenta accreta
• Death
• Emergency hysterectomy
Fetal risks
• Hypoxic Ischemic Encephalopathy
• Stillbirth
• Perinatal death
• Neonatal death
• Respiratory morbidity
• Transient tachypnea
• Hyperbillirubinemia
The probability that a woman attempting TOLAC will achieve VBAC depends on her individual combination of factors.
Selected Clinical Factors Associated with Trial of Labor after Previous Cesarean Delivery Success
Increased Probability of Success
• Prior vaginal birth
• Spontaneous labor
Decreased Probability of Success
• Recurrent indication for initial cesarean delivery (labor dystocia)
• Increased maternal age
• Non-white ethnicity
• Gestational age greater than 40 weeks
• Maternal obesity
• Preeclampsia
• Short interpregnancy interval
• Increased neonatal birth weight
(8) http://www.webmd.com/baby/tc/vaginal-birth-after-cesarean-vbac-risks-of-vbac-and-cesarean-deliveries