Vaginal prolapse, also called pelvic organ prolapse, occurs when an organ in the pelvis (e.g., uterus, urethra, bladder) or the top portion of the vagina (called the vaginal vault) drops down into or protrudes through (herniates) the vagina. Muscles, ligaments, and other structures around the vagina help support the pelvic organs, keeping them in place. Vaginal prolapse can occur when this support system weakens or is damaged.