A 36-year-old woman presents at 39 weeks of gestation for a…

A 36-year-old woman presents at 39 weeks of gestation for a scheduled prenatal visit. The patient had a cesarean delivery in a prior pregnancy, which was complicated by postpartum hemorrhage. The patient asks the clinician if she could give birth through a spontaneous vaginal delivery. The clinician plans a trial of labor after cesarean section (TOLAC) for this patient. Which of the following is the most significant complication of this trial of labor?