You have a scar on your uterus from a previous cesarean delivery. It is located on the lower part of your uterus, which does not contract very much during labor. But there is a chance that this scar may separate during labor, because of the stress from the uterus stretching.
The scar opens up in about 2 out of 100 women who attempt a VBAC. In most women who have a scar that opens up, the uterus does not rupture, and if there are problems, they are minor. But if it ruptures, there is an increased risk to you and your child. This causes serious problems in about 1 out of every 250 women who have a VBAC.
The risk of uterine rupture gets higher with the number of cesareans you have already had.