A pessary is a rubber device that fits into your vagina to help support your uterus (womb), vagina, bladder, or rectum.The pessary is most often used to treat prolapse of the uterus. Prolapse refers to when the uterus drops or “falls out” because it loses support after childbirth or pelvic surgery. pessary is a rubber device that fits into your vagina to help support your uterus (womb), vagina, bladder, or rectum.