Third and fourth degree perineal tears. Predictor factors in a referral hospital. Acta Obstet Gynecol Scand. 2001 Mar;80(3):229-34.

Study to determine the predictive factors of third and fourth degree perineal tears. Predictive factors: nulliparity, crouching position on low chair, maternal age > 35 years, baby points > 4000g, median episiotomy, oxytocin acceleration and birth between 3am and 6am.