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Updated: Sep 27, 2025

Anogenital Distance and Perineal Measurements of the Pelvic Organ Prolapse POP Quantification System
Published on: September 20, 2018
Influence of previous delivery mode on perineal trauma risk
Elizabeth P C Thorne1, Constantin M Durnea2, Philip M Sedgwick1
1Institute of Medical and Biomedical Education, St George's, University of London, London, UK.
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.
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