Induction or augmentation of labor with oxytocin has been implicated in increased rates of uterine rupture in women undergoing TOLAC (Zelop, 1999). In the Network study reported by Landon and colleagues (2004), uterine rupture was more frequent in women induced with oxytocin alone-I.l percentthan in those in spontaneous labor-O.4 percent. Augmentation of labor was associated with uterine rupture in 0.9 percent. Among women in this trial without a prior vaginal delivery, the uterine rupture risk associated with oxytocin induction was 1.8 percent-a fourfold greater risk compared with spontaneous labor (Grobman, 2007a). In contrast, in one case-control study, induction was not associated with a higher risk for rupture (Harper, 2012a). Cahill (2008) and Goetzl (2001) and their coworkers reported a dose-related risk of rupture with oxytocin.
Various prostaglandin preparations commonly employed for cervical ripening or labor induction are discussed in Chapter 26 (p. 506). s a group, their safe use in women with a prior cesarean delivery is unclear because of conlicting data.
With misoprostol (PGE1), Wing and colleagues (1998)
FIGURE 31-4 Neonatal morbidity rates seen with 13,258 elective repeat cesarean deliveries. Any adverse outcome includes death. Sepsis includes suspected and proven. RDS = respiratory distress syndrome; IN = transient tachypnea of the newborn. (Data from Tita AT, Landon MB, Spong CY, et al: Timing of elective repeat cesarean delivery at term and neonatal outcomes. N Engl J Med 360(2):1o11,o2009.) compared it versus oxytocin for labor induction in women with a prior cesarean delivery. They terminated their trial after two of the irst 17 women assigned to misoprostol developed a uterine rupture. Other studies confirmed this, and most consider misoprostol to be contraindicated (American College of Obstetricians and Gynecologists, 2017 a).
Of other prostaglandins, studies to evaluate their use for induction are contradictory. Ravasia and coworkers (2000) compared uterine rupture in 172 women given PGE2 gel with 1544 women in spontaneous labor. The rupture rate was significantly greater in women treated with PGE2 gel-2.9 percent compared with 0.9 percent in those with spontaneous labor. Lydon-Rochelle and associates (2001) found similar results. However, in the Network study cited previously, the uterine rupture rate was 1.4 percent when any prostaglandin was used in combination with oxytocin (Landon, 2004). But, in the subgroup of 227 women in whom labor was induced with a prostaglandin alone, there were no ruptures. Similar findings were reported with intravaginal prostaglandins, which were not associated with a greater uterine rupture risk (Macones, 2005b). These latter investigators, along with Kayani and colleagues (2005), found that sequential use of a prostaglandin followed by oxytocin was associated with a threefold greater risk of rupture compared with spontaneous labor.