Interdelivery interval and uterine rupture.

OBJECTIVE: The purpose of this study was to measure the impact of the interdelivery interval on uterine rupture during subsequent delivery.

STUDY DESIGN: An observational cohort study was performed to assess the rate of uterine rupture in women with a previous low transverse cesarean delivery and no previous vaginal delivery who undergo a trial of labor from 1988 to 2000 in a tertiary care center. The rate of uterine rupture was measured for each of the following interdelivery intervals: <or=12 months of gestation, 13 to 24 months of gestation, 25 to 36 months of gestation, and >36 months of gestation. Multivariate logistic regression analysis was used to adjust for selected confounding variables.

RESULTS: Of the 1527 women who met the study criteria, the rate of uterine rupture was 4.8% for patients with an interdelivery interval of <or=12 months of gestation, 2.7 % for patients with an interval between 13 and 24 months of gestation, 0.9% for patients with an interval between 25 and 36 months of gestation, and 0.9% for patients with an interval of >36 months of gestation (P =.04). After adjustment for the confounding variables, the odds ratio for uterine rupture in women with an interdelivery interval of <or=24 months of gestation was 2.65 (95% CI, 1.08-6.46) and 4.33 (95% CI, 1.70-10.98) in women with a single-layer closure of the previous uterine incision. The combination of an interdelivery interval of <or=24 months of gestation and a single-layer closure of the previous uterine incision were associated with a rate of uterine rupture of 5.6%.

CONCLUSION: An interdelivery interval of <or=24 months of gestation was associated with a 2- to 3-fold increase in the risk of uterine rupture compared with an interval of >24 months of gestation.