Postpartum lower abdominal pain or vaginal swelling is a manifestation of uterine involution. The degree of uterine involution varies, ranging from postpartum lower abdominal pain or vaginal swelling in mild cases to painful shock in severe cases. The majority of uterine inversions are due to improper management of the third stage of labor (about 50%), but the prerequisites must be the presence of uterine wall relaxation and cervical dilatation. The causes of uterine inversion are: 1. The result of the midwife forcibly pulling the umbilical cord of the placenta attached to the bottom of the uterus, when the umbilical cord is tough and does not break from the placenta, plus the forceful snap pressure on the loose bottom of the uterus will cause uterine inversion. 2, the umbilical cord is too short or twisted fetus delivery process, excessive pulling the umbilical cord will also cause uterine involution. 3, congenital uterine dysplasia or maternal over-weakness, during labor due to coughing or the second stage of labor force to hold the breath, the abdominal pressure rises, will also cause uterine inversion. 4, maternal standing delivery Because of the fetal weight on the placenta umbilical cord pulling action, and cause the uterus inversion. 5, the use of magnesium sulfate to relax the uterus during hyperemesis, will also contribute to uterine inversion. There are reports of implantation of the placenta will also contribute to the inversion of the uterus.