Pearl 4Risk of rupture is greater with oxytocin induction
Women with a prior cesarean delivery face an increased risk of uterine rupture with labor induction.8,9 Zelop et al8 demonstrated that labor induction with oxytocin is associated with a 4- to 5-fold increased risk of uterine rupture compared to spontaneous labor.
Lydon-Rochelle et al9 reported an increased risk of uterine rupture for those in spontaneous labor and those induced without prostaglandins, compared with women opting for elective repeat cesarean. The odds ratios for patients with spontaneous labor (3.3; 95% confidence interval [CI] 1.8-6.0) and for those with labor induced without prostaglandins (4.9; 95% CI 2.4-9.7) were not statistically significantly different.
Recent trials have suggested that induction of labor is not associated with uterine rupture, though these studies are limited by relatively low numbers of patients. Delaney and Young10 reported rates of uterine rupture of 0.7% for those with induced labor as compared to 0.3% for those with spontaneous labor (P = 0.1). By combining these studies, we see a statistically significant increased rate of uterine rupture approximately twice that of those in spontaneous labor.11
Oxytocin can be used judiciously for augmentation of labor for women with prior cesarean delivery, as it is not associated with an increased risk for uterine rupture in these cases.8
Pearl 5Prostaglandins should not be used for cervical ripening or induction
For patients with a prior cesarean delivery, prostaglandins used for cervical ripening are associated with a significantly higher rate of uterine rupture compared with repeat cesarean, and with either spontaneous labor or induction with oxytocin alone.9
Lydon-Rochelle et al9 demonstrated a 15.6 relative risk (95% CI 8.1-30.0) for uterine rupture among women having labor induced with prostaglandins, compared with those undergoing elective repeat cesarean.
Women with a prior vaginal delivery were 5 times less likely to suffer uterine rupture than those with no prior vaginal deliveries.
‘Once a cesarean, always a cesarean’? Shifting views on the role of VBAC
Because much literature has documented an increased risk of uterine rupture with misoprostol use in women with a prior uterine scar, the American College of Obstetricians and Gynecologists Committee on Obstetric Practice advises against using this agent during trial of labor after cesarean.12At the beginning of the 20th century, Cragin wrote a dictum that is still invoked: “Once a cesarean, always a cesarean.”24
Not often mentioned, however, is that he went on to discuss a patient who had 3 successful vaginal births after cesarean “without difficulty.”24
For much of the 20th century, vaginal birth after cesarean (VBAC) was the exception rather than the rule. Then, 25 years ago, the National Institutes of Health advocated a trial of labor for women who had a prior cesarean delivery. During this time, VBAC was greatly encouraged, and the rate of trials of labor after cesarean began to increase.25 Thus, 15 years ago, the cesarean delivery rate in the United States began to fall after an unprecedented rise during the previous decades.
A few years later, however, this trend ceased and the cesarean delivery rate once again began to rise. This switch can be attributed to both an increase in primary cesarean deliveries and a decrease in the VBAC rate.26 It coincides with published data on uterine rupture associated with a trial of labor after cesarean: Two case series published in 1991 together documented 20 uterine ruptures with 4 perinatal deaths, 4 neonates with neurological impairment, and 3 women who underwent hysterectomy due to the event.27,28
Further study is needed to more precisely identify those women at high risk for uterine rupture and low risk of success of a trial of labor, and also—perhaps more importantly—those women with a very low risk of uterine rupture and a high likelihood of success with a trial of labor. Perhaps such additional research will help reverse the current malpractice climate, which is influencing the move by many physicians away from VBAC.
Pearl 6More than 1 prior cesarean increases risk of rupture
The presence of multiple prior cesarean scars places a woman at greater risk for uterine rupture during trial of labor. This risk is likely 3 to 5 times higher than for patients with only 1 prior cesarean delivery.13
Pearl 7Risk of rupture is increased with interdelivery interval of up to 18-24 months
Women who have undergone a cesarean delivery and are contemplating a future trial of labor should be discouraged from becoming pregnant for at least 9 months, possibly up to 15 months.
Interdelivery interval has been shown to be an important contributor to the risk for uterine rupture during trial of labor after cesarean.12-14 Esposito et al14 were the first to note an increased risk of uterine scar failure—including both symptomatic uterine ruptures and asymptomatic uterine scar dehiscences—for those with an interpregnancy interval of less than 6 months.