Interdelivery interval and risk of symptomatic uterine rupture.

OBJECTIVE: To relate interdelivery interval to risk of uterine rupture during a trial of labor after prior cesarean delivery.

METHODS: We reviewed the medical records of all women who had a trial of labor after cesarean delivery over 12 years (July 1984 to June 1996). Analysis was limited to women with only one prior cesarean delivery and no prior vaginal deliveries who delivered term singletons and whose medical records included the month and year of the prior delivery. The time in months between the prior cesarean delivery and the index trial of labor was calculated, and the women were divided accordingly to permit comparison with respect to symptomatic uterine rupture.

RESULTS: Two thousand four hundred nine women had trials of labor after one prior cesarean delivery and had complete data from the medical records. There were 29 uterine ruptures (1.2%) in the population. For interdelivery intervals up to 18 months, the uterine rupture rate was 2.25% (seven of 311) compared with 1.05% (22 of 2098) with intervals of 19 months or longer (P =.07). Multiple logistic regression was used to assess the risk of uterine rupture according to interdelivery interval while controlling for maternal age, public assistance, length of labor, gestational age at least 41 weeks, and oxytocin use. Women with interdelivery intervals of up to 18 months were three times as likely (95% confidence interval, 1.2, 7.2) to have symptomatic uterine rupture.

CONCLUSION: Interdelivery intervals of up to 18 months were associated with increased risk of symptomatic uterine rupture during a trial of labor after cesarean delivery compared with that for longer interdelivery intervals.