Perineal lacerations are categorized into the following four degrees according to the severity of the laceration:1. There is a laceration of the perineal skin and the mucous membrane of the vaginal opening, which is a degree I perineal laceration, and there is not much bleeding because the muscular layer has not been injured.2. Degree II perineal lacerations are those in which the laceration has already reached the muscular layer, and the mucous membrane of the posterior wall of the vagina has been torn, and there is a lot of bleeding, and the wounds are irregular, so that the original structure of the perineum is not easy to be identified.3. The external anal sphincter is ruptured, which belongs to degree III perineal laceration.4. If the vaginal rectal septum and the anterior wall of the rectum are torn, it is a perineal laceration of degree IV. Degree I and II perineal lacerations are more common in clinical practice, while degree III and IV perineal lacerations are more serious and difficult to suture.