Influence of previous delivery mode on perineal trauma risk

Objective To evaluate the impact of a previous pregnancy and delivery on perineal trauma rates in the subsequent vaginal birth. Methods Retrospective cohort study. The perineal outcomes of secundiparous women with history of previous (first) delivery in one of three categories: failed operative vaginal delivery (FOVD) and second-stage emergency cesarean section (EmCS); elective cesarean section (ElCS), and vaginal delivery (VD) with intact perineum, were compared with a control primiparous group. Results The percentage obstetric anal sphincter injuries (OASIS)at first vaginal delivery was 17.3% (n = 9) after previous FOVD+EmCS, 12.9% (n = 18) after previous ElCS, and 0.6% (n = 9) after previous VD maintaining an intact perineum, compared with 6% (n = 1193) in the control primiparous group of women. Multivariate regression analysis demonstrated that previous FOVD+EmCS and ElCS were associated with a statistically significant increased risk of OASIS of 180% and 110% when compared with control (odds ratio [OR] 2.80; 95% confidence interval [CI] 1.35-5.78 and OR 2.10; 95% CI 1.27-3.48, respectively). Previous VD with intact perineum was associated with a statistically significantly reduced risk of OASIS (OR 0.09; 95% CI 0.04-0.17). Conclusions Previous FOVD+EmCS and ElCS were associated with increased risk of OASIS in subsequent vaginal delivery compared with control, whereas previous VD with intact perineum was associated with decreased risk.

Automated summary

This study evaluated the impact of a previous pregnancy and delivery on perineal trauma rates in subsequent vaginal birth and found that failed operative vaginal delivery and second-stage emergency cesarean section were associated with increased risk of OASIS, while previous vaginal delivery with intact perineum was associated with decreased risk of OASIS.