A menstrual cup is a flexible, reusable feminine hygiene product, typically made of medical-grade silicone, that is folded and inserted into the vaginal canal to collect menstrual fluid. When used correctly, cups should not leak, as they are designed to form a secure seal against the vaginal walls. Leakage is almost always a symptom of user error, such as incorrect placement, a poor fit, or a failure to create the necessary seal.
The Primary Causes of Leakage
One of the most frequent causes of leakage is the failure of the cup to fully open and form a proper suction seal once it is inside the body. If the cup remains partially folded or creased, it creates a small channel that allows fluid to bypass the collection area and escape.
Incorrect placement relative to the cervix is another major factor that leads to unexpected leaks. The cup is designed to sit low in the vaginal canal, positioned directly beneath the cervix to catch the flow as it exits the uterus. If the cup is pushed too high, it may settle in the wider part of the vaginal fornix and shift, causing the flow to run down the outside of the cup. Conversely, if the cup is sitting too low, it can cause discomfort and break the seal.
The position of the cervix itself can also interfere with the cup’s function. If the cervix dips into the cup, it can occupy significant space, reducing the cup’s effective capacity. This displacement can cause the cup to overflow well before it appears full upon removal, resulting in a leak.
Leaks can occur because the cup has reached its holding capacity, especially on heavy flow days. If left in too long, the collected fluid will eventually overflow the rim. The suction holes near the rim can also become clogged, which prevents the cup from maintaining the necessary vacuum seal against the vaginal walls.
Mastering Proper Insertion
Achieving a successful seal begins with the folding technique used for insertion, such as the C-fold or the punch-down fold. The punch-down fold often results in a smaller insertion point and a firmer rim, which can aid in opening once inside. The cup should be inserted horizontally, aiming toward the tailbone rather than straight up, following the natural curve of the vaginal canal.
Once the cup is fully inserted, ensure it has completely unfolded and created the vacuum seal. The cup should be pushed in until the base is comfortable to reach, but the rim is seated securely below the cervix. Check for a proper seal by running a clean finger around the base of the cup to confirm there are no folds or dents.
Rotating the cup a full 360 degrees or giving the base a slight squeeze can help encourage the rim to fully expand against the vaginal walls. If you lightly tug on the stem and feel resistance, the suction is holding the cup in place. Properly seated, the cup should feel comfortable and not cause any pain.
For removal, first break the suction seal before pulling the cup out. This is done by pinching the base of the cup or sliding a finger along the rim to allow air to enter. Breaking the seal prevents discomfort and avoids the sudden release of suction that can cause spills or splashes.
Selecting the Right Size and Firmness
While proper technique is essential, it cannot overcome a mismatch between the cup and the user’s anatomy. The physical dimensions of the cup, specifically its length and width, must align with the individual’s body. Cervix height is a primary factor in cup length selection; a person with a low cervix needs a shorter cup, while a high cervix requires a longer cup for easy retrieval.
The volume of menstrual flow dictates the necessary capacity of the cup. Those with a heavy flow should opt for a larger cup diameter to extend the time between emptying. Using a cup with insufficient capacity will necessitate frequent emptying and increase the risk of overflow leaks.
Pelvic floor muscle strength is another consideration. Individuals with strong pelvic floor muscles may require a firmer cup to resist being pinched or compressed, which could otherwise break the seal. Conversely, a softer cup may be more comfortable for those with sensitive bladders or weaker pelvic floor tone.
Finding the right menstrual cup is often a process of trial and error, as no universal sizing standard exists across all brands. Evaluating these physical factors—cervix height, flow volume, and pelvic floor strength—provides a targeted starting point. Choosing the wrong size or firmness is a common reason for persistent leaks that insertion practice cannot fully resolve.