Trends in major modifiable risk factors for severe perineal trauma, 1996–2006

Objective: To examine what effect the major modifiable risk factors for severe perineal trauma have had on the rates of this trauma over time. Methods: A retrospective observational cohort study of singleton vaginal deliveries taken from a perinatal database for the period 1996 through 2006. Results: A total of 46 239 singleton vertex vaginal deliveries met the inclusion criteria. Major risk factors for severe perineal trauma were increased maternal age (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.1–1.5), non-African American ethnicity (OR 1.5, 95% CI 1.3–1.7), nulliparity (OR 4.8, 95% CI 4.11–5.6), fetal birth weight (OR 2.2, 95% CI 1.9–2.4), forceps (OR 8.3, 95% CI 5.4–10.8), vacuum (OR 2.9, 95% CI 1.9–4.4), and midline episiotomy (OR 5.7, 95% CI 5.0–6.4). Evaluation of the changes in rates of these factors over the study period revealed that the decline in the rates of episiotomy and the use of forceps accounted for a reduction in severe lacerations of more than 50%. Conclusion: Reduction of severe perineal trauma by restricted use of the 2 modifiable clinical variables, episiotomy and forceps, is evident over time.