According to the American College of Obstetricians and Gynecologists, you're a good candidate for a vaginal birth after a c-section if you meet all of the following criteria:
You've had only one previous cesarean delivery and it was done with a low transverse (horizontal) incision. Having had more than one c-section or an incision in your upper uterus that was vertical — also known as "classical" — or T-shaped puts you at a greatly increased risk for uterine rupture. Note that the type of scar you have on your belly may not match the one on your uterus, so your practitioner will need to review a copy of your c-section report.
Your pelvis seems large enough to allow your baby to pass through safely. (While there's no way to know this for sure, your practitioner can examine your pelvis and make an educated guess.)
You've never had any other extensive uterine surgery, such as a myomectomy to remove fibroids.
You've never had a uterine rupture.
You have no medical condition or obstetric problem that would make a vaginal delivery risky.
There's a physician on site who can monitor your labor and perform an emergency c-section if necessary.
There's an anesthesiologist, other medical personnel, and equipment available around-the-clock to handle an emergency situation for you or your baby.
VBACs are controversial, and you may find it difficult to decide whether to attempt one. The best approach is to talk to your practitioner about your individual chance of success. Start the discussion early in pregnancy so you'll have time to carefully weigh the benefits and risks.