Effect of interpregnancy interval on the success rate of trial of labor after cesarean.

OBJECTIVE: The objective of this study is to investigate the association between interpregnancy interval and success of vaginal birth after cesarean.

STUDY DESIGN: Retrospective 10-year cohort study of pregnant women with one prior cesarean, who opted for trial of labor (n=36 653). Interpregnancy interval is the time between cesarean and next conception. Vaginal birth success rates were compared between six interval groups. Analysis was performed pooled as well as stratified for induction of labor. Adjusted odds ratios were calculated.

RESULTS: Success rate in the reference group (12 to 24 months) was 72%. Success rates were similar among those with an interval of less than 24 months. Intervals of 24 months or more showed a decrease in success rate; 70% in 24- to 35-month intervals (adjusted odds ratio 0.92 (0.87 to 0.98)), 67% in 36- to 59-month intervals (adjusted odds ratio 0.87 (0.81 to 0.94)) and 62% in intervals of more than 60 months (adjusted odds ratio 0.77 (0.67 to 0.88)).

CONCLUSION: An interpregnancy interval of <24 months is not associated with a decreased success of vaginal birth after cesarean. Success rates decrease when interval increases.