Objective: To investigate whether short or long interpregnancy interval is associated with uterine rupture and other major maternal morbidities in women who attempt vaginal birth after cesarean delivery (VBAC).
Methods: We performed a secondary analysis of a U.S. multi-center, record-based, retrospective cohort study of 13,331 pregnant women, identified by a validated International Classification of Disease, 9th Revision, code search, with at least one prior cesarean delivery, who attempted VBAC between 1995 and 2000. We performed univariable and multivariable logistic regression analyses to evaluate the association between long or short interpregnancy interval and three maternal outcomes: 1) uterine rupture, 2) composite major morbidity (including rupture, bladder or bowel injury, and uterine artery laceration), and 3) blood transfusion. We evaluated short interpregnancy interval with cutoffs at less than 6, less than 12, and less than 18 months between prior delivery and conception and defined long interval as 60 months or more.
Results: A total of 128 cases (0.9%) of uterine rupture occurred, and 286 (2.2%), 1,109 (8.3%), 1,741 (13.1%), and 2,631 (19.7%) women had interpregnancy intervals of less than 6, 6-11, 12-17, and 60 months or more, respectively. An interval less than 6 months was associated with increased risk of uterine rupture (adjusted odds ratio [aOR] 2.66, 95% confidence interval [CI] 1.21-5.82), major morbidity (aOR 1.95, 95% CI 1.04-3.65), and blood transfusion (aOR 3.14, 95% CI 1.42-6.95). Long interpregnancy interval was not associated with an increase in major morbidity.
Conclusion: Short interpregnancy interval increases risk for uterine rupture and other major morbidities twofold to threefold in VBAC candidates.
Level of evidence: II.