Materials and Methods: A subset analysis of women with spontaneous vaginal deliveries (n=489) from an institutional review board-approved parent study in healthy, nulliparous, continent pregnant women, attending the public health care system of Catalonia (northeast Spain). Primary outcome measure was perineal trauma according to the RCOG classification. For the bivariate analysis, the Student?s t-test, ANOVA and the chi-squared test, or the corresponding non-parametric tests were used. Rates, relative risks and odds ratios (multivariate analysis) were estimated along with 95% confidence intervals (CI).

Results: About 91% (95% CI: 88-93%) of women with vaginal deliveries showed some degree of perineal trauma. Nulliparous women with spontaneous deliveries who did not undergo an episiotomy were 9 times more likely to present a tear (any grade) than those who received an episiotomy [Relative risks (RR) = 9.6, 95% CI: 6.3%-14.6%, P<0.001]. Only episiotomy reached statistical significance in bivariate and multivariate analyses (P<0.0001), revealing the protective effect of episiotomy respect to second-degree tear.

Conclusion: The absence of episiotomy was the only variable independently associated with second degree perineal tears, showing a clear protective effect.