The uterus, or womb, is a muscular structure that's held in place by pelvic muscles and ligaments.
If these muscles or ligaments stretch or become weak, they're no longer able to support the uterus, causing prolapse.
Uterine prolapse occurs when the uterus sags or slips from its normal position and into the vagina, or birth canal.
Uterine prolapse may be incomplete or complete. An incomplete prolapse occurs when the uterus is only partly sagging into the vagina. A complete prolapse describes a situation in which the uterus falls so far down that some tissue rests outside of the vagina.