A menstrual disc is a flexible, circular barrier device inserted into the vagina to collect menstrual fluid instead of absorbing it. Unlike traditional menstrual cups, which sit lower in the vaginal canal and use suction, the disc rests higher up in a wider space. This unique positioning enables the phenomenon often referred to as “self-emptying” or “passive emptying.” This partial release of fluid occurs due to the disc’s interaction with internal anatomy and muscle movements.
Placement Facilitates Passive Emptying
The disc’s ability to self-empty is a direct result of its specific anatomical placement. When inserted correctly, the flexible ring is tucked high up into the vaginal fornix, the widest part of the canal just below the cervix. The front rim is secured firmly behind the pubic bone, which acts as a shelf to keep the device in position without relying on suction.
Because the disc spans the width of the canal and rests so high, the collected fluid is held in a reservoir above the pelvic floor muscles. The disc is held in place by bone and tissue tension rather than by a strong vacuum seal. When external pressure is applied, this unique setup allows for a momentary shift that can break the seal during routine bathroom use.
Physical Actions That Trigger Emptying
The core of the self-emptying action is the temporary displacement of the disc’s rim caused by specific muscle engagement. This usually happens when the user is seated on a toilet and engages the abdominal and pelvic floor muscles, such as when urinating or having a bowel movement. Bearing down or straining causes a downward shift in the internal organs, which temporarily pushes the cervix and the back of the disc lower into the vaginal canal. This downward pressure causes the front rim of the disc to momentarily dislodge or tilt slightly away from the pubic bone.
The brief loss of the seal allows the collected menstrual fluid to pour out into the toilet bowl, often in a quick gush. Once the pressure from the muscle engagement is released, the pelvic floor and internal structures relax and return to their original position. The flexible rim of the disc typically snaps back into place behind the pubic bone, resealing the device to continue collecting fluid.
When Manual Removal Is Still Necessary
Self-emptying is not a substitute for the required manual removal and cleaning of the disc. Passive emptying typically only releases a portion of the collected fluid, especially for those with a heavier flow. The manufacturer-recommended wear time of up to 12 hours still requires the user to remove the disc completely for proper hygiene. For those who do not experience the action automatically, it can sometimes be initiated by gently bearing down while seated on the toilet, or by squatting or leaning forward slightly.
If any leakage is noticed outside of bathroom use, it suggests an improper fit or that the disc is full and needs manual removal. Leakage is a sign of potential overflow, whereas passive emptying is a controlled partial release that happens only when the user is actively on the toilet.