A number of factors related note: vacumm aspiration (PR=5.6, 95% CI (3.13 to 10.04)), forceps deliveries (PR=10.31, 95% CI (4.11 to 28.86)), birth weight ≥ 3800g (PR=2.25, 95% CI (1.09 to 5.84), non-nulliparous women (PR=0.55, 95% CI (0.36 to 0.86)), no epidural anesthesia (PR=0.165 95% CI (0.1-.25)), no insertion of Foley catheter (PR=2.56, 95% CI (1.55 to 4.22)), no perineal trauma (PR=0.18, 95% CI (0.08 to 0.4)).