The soft birth canal includes the lower uterine segment, cervix, vagina and vulva. Lesions in the soft birth canal itself can cause obstructed labor, and lesions in and around other parts of the genital tract can also affect the soft birth canal and make labor difficult, but the former is more common. The obstructed labor due to soft birth canal anomaly is much less common than that due to bony birth canal anomaly, so it is easy to be overlooked and cause missed diagnosis. Soft birth canal anomalies are those in which the uterine opening, vagina and vulva are tough and not sufficiently extended, making it difficult for the fetus to pass. Soft birth canal anomalies should be diagnosed differently from soft birth canal tears, which are a series of changes in the soft birth canal during pregnancy to adapt to labor, such as the tissue becoming loose and soft, with increased elasticity and a certain degree of stretching. Despite these changes, the degree of dilation required to deliver the fetus through the birth canal is greater, and most women, especially primiparous women, are still at risk for varying degrees of injury to the cervix, vagina and perineum during delivery. The term birth canal laceration here refers to the laceration of the soft birth canal that occurs during labor. Soft birth canal tears are caused by strong contractions of the uterus, rapid progress of labor, and oversized fetus, which often result in lacerations of the cervix and/or vagina before the fetus is delivered. Improper protection of the perineum and improperly performed assisted labor can also result in perineal and vaginal lacerations. A small perineal incision may result in severe perineal laceration during delivery, and premature lateral perineal incision may also result in excessive bleeding from the incision. Severe perineovaginal lacerations can extend upward to the fornix, the paravaginal space, or even deep into the pelvic wall, and the deep vaginal area near the fornix is severely torn and the hematoma can extend upward into the broad ligament. Minor cervical lacerations are almost inevitable during delivery and are usually not diagnosed as cervical lacerations because they are shallow and do not bleed significantly. The more hemorrhagic cervical lacerations occur when the fetus passes too quickly through an incomplete cervix and in severe cases may involve the vaginal vault downward and extend upward to the lower part of the uterus, resulting in massive bleeding.