Objective: We sought to assess the modern prevalence and risk factors for third- and fourth-degree perineal tears.
Study design: The study population comprised 38,252 women who delivered in one medical center, from January 2005 through December 2009, and met the following inclusion criteria: singleton pregnancy, vertex presentation, and vaginal delivery. Of these, 96 women (0.25%) sustained third- or fourth-degree perineal tears. Maternal and obstetric variables were compared between women with vs without severe perineal tears.
Results: Five variables were found to be statistically significant independent risk factors: Asian ethnicity (odds ratio [OR], 8.9; 95% confidence interval [CI], 4.2-18.9), primiparity (OR, 2.4; 95% CI, 1.5-3.7), persistent occipito posterior (OR, 2.1; 95% CI, 1-4.5), vacuum delivery (OR, 2.7; 95% CI, 1.6-4.6), and heavier birthweight (OR, 1.001; 95% CI, 1-1.001).
Conclusion: Severe perineal tears are uncommon in modern obstetric practice. Significant risk factors are Asian ethnicity, primiparity, persistent occipito posterior, vacuum delivery, and heavier birthweight.
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