Women who have a first birth by cesarean section are at increased risk of suffering uterine rupture if they try to deliver their second infant vaginally, especially if labor is induced with prostaglandins, according to evidence from a population-based study in Washington State.1 In a retrospective cohort analysis of more than 20,000 women whose first infant had been delivered by cesarean, only 91 (or 4.5 per 1,000) suffered uterine rupture during their second delivery. However, the risk was elevated among those who had a vaginal second delivery and was particularly high--24.5 per 1,000--among those with prostaglandin-induced labor. As the investigators point out, the issue of whether a woman should attempt to deliver vaginally after having a cesarean has created concern for decades, and previous studies have yielded inconsistent findings about the associated risk of complications.
The researchers used a statewide database that links birth records with maternal and infant hospital-discharge records to identify women who had their first two births between 1987 and 1996, and whose first delivery was by cesarean. This data set permitted them to distinguish the risk of uterine rupture associated with different labor and delivery experiences. Their analyses are based on 20,095 women, of whom 54% went into labor spontaneously before delivering their second baby, 35% had a repeat cesarean and the rest had labor induced, 10% without and 2% with prostaglandins.
Overall, uterine rupture was uncommon, occurring among 4.5 women per 1,000 (91 women). Women who underwent a repeat cesarean had the lowest risk (1.6 ruptures per 1,000 women); the risk was somewhat higher among women whose second labor began spontaneously (5.2) or was induced without prostaglandins (7.7) and was markedly higher among those who had prostaglandin-induced labor (24.5). The investigators calculated the relative risks of this complication for the four subgroups, and found that women who had spontaneous labor or induced labor without prostaglandins were about 3-5 times as likely as those who had a repeat cesarean to experience uterine rupture (relative risks, 3.3 and 4.9, respectively). Those who had prostaglandin-induced labor, however, were nearly 16 times as likely to suffer this complication (15.6).
Women whose uterus ruptured were more likely than others to experience a number of complications after the birth of their second infant. For example, 6% experienced infant death; 8-11% had a bladder injury, an infection or posthemorrhagic anemia; 26% were hospitalized for more than five days; and 35% suffered surgical complications. By contrast, no more than 5% of women without uterine rupture had these experiences.
According to the researchers, their use of longitudinally linked data represented a major strength of their study: It increased the accuracy and completeness of information on obstetric diagnoses and interventions, and enabled them to examine a large number of occurences of a rare outcome. Their ability to include women who had a repeat cesarean as a comparison group, they add, further improves over the design of earlier studies of this issue and bolsters their conclusion that induction of labor increases the risk of uterine rupture among women who have previously had a cesarean section, particularly if induction involves the use of prostaglandins.
The author of an editorial accompanying the study notes that some women who have had a cesarean section may conclude that the absolute risks of uterine rupture and further complications if they subsequently try to deliver vaginally "are so small that they are worth taking and are outweighed by the benefits of a successful vaginal birth." However, he emphasizes that "these issues must be discussed with each patient, and she must make that decision for herself."2--D. Hollander
1. Lydon-Rochelle M et al., Risk of uterine rupture during labor among women with a prior cesarean delivery, New England Journal of Medicine, 2001, 345(1):3-8.
2. Greene MF, Vaginal delivery after cesarean section--is the risk acceptable? editorial, New England Journal of Medicine, 2001, 345(1):54-55.