Lacerations of the birth canal are common side effects of vaginal birth. They are potentially preventable. Although serious long-term consequences have been identified for severe perineal
lacerations, less attention has been paid to
lacerations in other locations and how the risk factors vary for different
lacerations. We analyzed a dataset including 1009 primiparous women with singleton pregnancies and vaginal deliveries, and we examined risk factors for third- and fourth-degree perineal
lacerations and periurethral, vaginal, and labial
lacerations using logistic regression analysis. Large fetal size (> or = 3500 g) substantially increased the risk of perineal (odd ratio [OR], 3.8; 95% confidence interval [CI], 1.8 to 7.9) and periurethral (OR, 2.3; 95% CI, 1.0 to 5.0)
lacerations but not other types of
lacerations.
Episiotomy had no impact on perineal
lacerations (OR 0.9) but had very strong protective effects for other
lacerations (OR 0.1). Prolonged second stage of labor (> 120 minutes) increased the risk of perineal and vaginal
lacerations but reduced the risk for periurethral
lacerations. Instrumental deliveries were significant risk factors for third- and fourth-degree perineal
lacerations, with by far the strongest effect for low
forceps (OR 25.0 versus < 3 for outlet
forceps, outlet vacuum, and low vacuum). We concluded that separating different birth canal
lacerations is critical in identifying risk factors and potential preventive strategies.