It also has been associated wiht classic uterine scars, ofen occuring without labor. Conversely, uterine dehiscence in partial separation of the uterine wall that is usually asymptomatic and rarely contributes to fetal or maternal morbidity. This is often the type of separation seen in lower segment scars, and usually occurs during labor. Ocften asymptomatic windows are incidentally noted at the time of repeat cesarean section. However, the data are difficult to interpret.
Many studies fail to distinguish between rupture and dehiscence.
However, there is a large difference in the morbidity from these different types of scar separation. In reviews prior to 1987, encompassing almost 10,000 VBACs, there were no maternal deaths from rupture of either scar type. Of the three from lower segment rupture, all occurred over 20 years years ago in unmonitored patients. As such, VBAC is recommended for patients with previos lower segement incision. In addition, classic scars frequently separate before delivery, whereas lower segment scars tend to separate during delivery.