Risk of Uterine Rupture Associated With an Interdelivery Interval Between 18 and 24 Months

To estimate the association between interdelivery interval and uterine rupture in women with a previous cesarean delivery. Secondary analysis was performed in a retrospective cohort study of women who underwent a trial of labor after undergoing a previous cesarean delivery. Only singleton pregnancies with a trial of labor at term were included. Women with two or more previous cesarean deliveries or with a vaginal delivery between the cesarean delivery and the trial of labor were excluded. The rates of uterine rupture were compared among women with interdelivery intervals 24 months or longer (controls), 18-24 months, and fewer than 18 months. The chi2 test and multivariable logistic regression analysis were conducted. A P value of less than .05 was considered significant. A total of 1,768 women were included: 1,323 (74.8%) were 24 months or longer, 257 (14.5%) were 18-23 months, and 188 (10.6%) were fewer than 18 months. The rates of uterine rupture were 1.3%, 1.9%, and 4.8%, respectively (P=.003). After adjustment for confounding factors, an interdelivery interval shorter than 18 months was associated with a significant increase of uterine rupture (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.3-7.2), whereas an interdelivery interval between 18 to 24 months was not (OR, 1.1; 95% CI, 0.4-3.2). An interdelivery interval shorter than 18 months, but not between 18 and 24 months, should be considered as a risk factor for uterine rupture.