Uterine inversion is classified not only by the degree of inversion but by the time of onset as well. The uterine fundus that has inverted and lies within the endometrial cavity without extending beyond the external os is called an incomplete inversion. Complete inversion describes an inverted fundus that extends beyond the external os. A prolapsed inversion is one in which the inverted uterine fundus extends beyond the vaginal introitus. A total inversion, usually nonpuerperal and tumor related, results in inversion of the uterus and vaginal wall as well. In terms of onset of the inversion, acute describes the event occurring before cervical ring contraction. If the cervical ring has contracted, a subacute inversion has occurred. The inversion is classified as chronic if 4 weeks have elapsed before the event.