Postpartum lower abdominal pain or vaginal distension is a manifestation of uterine involution. The degree of uterine involution varies from mild, which can be manifested only as postpartum lower abdominal pain or vaginal distension, to severe, which can cause painful shock. The diagnosis of uterine involution can be made according to the history and examination. 1, abdominal examination: acute uterine inversion abdomen usually can not touch the regular uterine contour, the uterus is obviously lower and wider, the bottom of the uterus in the shape of a cup or ladder. Chronic uterine inversion can only show signs of peritonitis. 2, vaginal examination: acute uterine inversion vaginal bleeding varies. The placenta may or may not be detached, and those who are not detached are easier to diagnose. Placental detachment can be touched or seen soft spherical object stuffed with the birth canal or out of the vaginal opening, careful examination of the spherical object on the cervix around or found that the opening of the fallopian tube, can be clearly diagnosed. In chronic uterine involution, in addition to the manifestations of acute uterine involution, there are also manifestations of chronic inflammation, inflammatory vaginal discharge, ulceration, bleeding and erosion on the surface of the mass.