The association between the number of vaginal examinations during labor and perineal trauma: a retrospective cohort study

Purpose: To study the association between the number of vaginal examinations (VEs) performed during labor and subsequent severe perineal trauma. Methods: This is a retrospective cohort study. We included all women admitted to the delivery ward between 2008 and 2017, in active labor. Exclusion criteria included preterm deliveries (< 37 weeks), Cesarean deliveries and episiotomy during delivery. The primary outcome, severe perineal trauma, was defined as perineal tears grades 3–4. The cohort was divided into 4 groups, based on the number of VEs performed during labor: Group 1—up to two VEs (n = 4588), Group 2—three to four VEs (n = 5815), Group 3—five to six VEs (n = 4687), and Group 4—seven or more VEs (n = 7297). Results: Overall, 22,387 women were included in the study. The rate of severe perineal trauma in groups 1, 2, 3 and 4 was 0.4%, 0.1%, 0.8%, and 0.4%, respectively (p < 0.001). Performing five or more VEs during labor was associated with a higher risk of severe perineal trauma (0.26% vs. 0.53%, p < 0.01), as compared to four VEs or less. Using a logistic regression model, we found that performing five or more VEs during labor (aOR = 1.72 CI 95% (1.21–2.47), p < 0.001) or performing an instrumental delivery (aOR = 2.65 CI 95% (1.72–4.07), p < 0.001) were directly associated with the risk for severe perineal trauma. Applying epidural anesthesia showed an inverse association with severe perineal trauma (aOR = 0.54 CI 95% (0.38–0.77), p < 0.001). Conclusion: Performing five or more VEs during active labor is associated with an increased risk for severe perineal trauma.