Which Cesarean incision carries the greatest risk of subsequent uterine rupture with vaginal birth?

The midline vertical (classic) incision carries the greatest risk of subsequent uterine rupture if a woman chooses to have a vaginal birth after a cesarean section (VBAC). This type of incision involves cutting vertically through the uterus, and due to its location, it compromises a larger segment of the uterine muscle. This significantly increases the likelihood of uterine rupture during labor, especially when compared to other types of incisions, which tend to preserve more of the muscular structure.

In contrast, the low transverse incision, which is the most common and preferred incision type today, is made horizontally at the lower part of the uterus. This incision heals well, and the risk of rupture during later pregnancies or labor is much lower. The low vertical incision also has a moderate risk, but not as high as the classic incision, while the transverse vertical incision has characteristics that generally do not lend themselves to a significant risk increase in terms of successful VBAC. Thus, the classic incision is identified as the one that poses the greatest risk for subsequent uterine rupture during a trial of labor.