Menstrual cup
This article needs additional citations for verification. (February 2023) |
A menstrual cup is a menstrual hygiene device which is inserted into the vagina during menstruation. Its purpose is to collect menstrual fluid (blood from the uterine lining mixed with other fluids). Menstrual cups are made of elastomers (silicone rubbers, latex rubbers, or thermoplastic rubbers).[1][2] A properly fitting menstrual cup seals against the vaginal walls, so tilting and inverting the body will not cause it to leak.[3] It is impermeable and collects menstrual fluid, unlike tampons and menstrual pads, which absorb it.[4][5]
Menstrual cups come in two types. The older type is bell-shaped, often with a stem, and has walls more than 2mm thick.[6] The second type has a springy rim, and attached to the rim, a bowl with thin, flexible walls. Bell-shaped cups sit over the cervix, like cervical caps,[7] but they are generally larger than cervical caps[10] and cannot be worn during vaginal sex. Ring-shaped cups sit in the same position as a contraceptive diaphragm; they do not block the vagina and can be worn during vaginal sex.[11][12] Menstrual cups are not meant to prevent pregnancy.
Every 4–12 hours (depending on capacity and the amount of flow), the cup is emptied (usually removed, rinsed, and reinserted). After each period, the cup requires cleaning.[13] One cup may be reusable for up to 10 years, making their long-term cost lower than that of disposable tampons or pads, though the initial cost is higher. As menstrual cups are reusable, they generate less solid waste than tampons and pads, both from the products themselves and from their packaging.[14] Bell-shaped cups have to fit fairly precisely; it is common for users to get a perfect fit from the second cup they buy, by judging the misfit of the first cup. Ring-shaped cups are one-size-fits-most, but some manufacturers sell multiple sizes.[15]
Reported leakage for menstrual cups is similar or rarer than for tampons and pads.[14] It is possible to urinate,[16] defecate, sleep, swim,[3] do gymnastics,[17] run, ride bicycles[18] or riding animals, weightlift, and do heavy exercise while wearing a menstrual cup.[17] Incorrect placement or cup size can cause leakage.[14] Most users initially find menstrual cups difficult, uncomfortable, and even painful to insert and remove. This generally gets better within 3–4 months of use; having friends who successfully use menstrual cups helps, but there is a shortage of research on factors that ease the learning curve. Menstrual cups are a safe alternative to other menstrual products; risk of toxic shock syndrome infection is similar or lower with menstrual cups than for pads or tampons.[14]
Terminology[edit]
The terminology used for menstrual cups is sometimes inconsistent. This article uses "menstrual cup" to mean all types, and for clarity, distinguishes the two main types as "bell-shaped" and "ring-shaped".
The thick-walled bell-shaped cups are the older type, and the term "menstrual cup" is sometimes used to refer only to bell-shaped cups. But in modern formal contexts, such as academic research[18] and regulations,[19] "menstrual cup" usually refers to both types.
The US Food and Drug Administration holds that "A menstrual cup is a receptacle placed in the vagina to collect menstrual flow."[20] The EU legislated that "The product group ‘reusable menstrual cups’ shall comprise reusable flexible cups or barriers worn inside the body whose function is to retain and collect menstrual fluid, and which are made of silicone or other elastomers."[21]
Ring-shaped cups are also called "menstrual discs" and sometimes "menstrual rings",[22] to distinguish them from bell-shaped cups. Bell-shaped cups are sometimes called "menstrual bells".[23]
Because bell-shaped cups are commonly depicted as being placed in the vaginal canal, well below the cervix, they are also called "vaginal cups", with the ring-shaped cups called "cervical cups". This may not clearly reflect their position in the body. MRI imaging suggests that, contrary to some manufacturer's depictions, the bell-shaped cups called "vaginal cups" are placed over the cervix, in a position similar to a cervical cap (not to be confused with a cervical cup).[7] Ring-shaped cups, called "cervical cups", also cover the cervix, but have one edge next to the cervix, and the other located further down the vagina, so that the cup is nearly parallel to the long axis of the vagina.[24]
In the 1800s, menstrual cups were called "'catamenial sacks",[25] and were similar external catamenial sacks of "canoe-like form",[26] which in turn were similar to catamenial sacks which were waterproof rubber undersheet supports for absorbent pads.[27] These were made from india-rubber or gutta-percha, forms of latex.[26]
Use[edit]
Menstrual cups are favoured by backpackers and other travellers, as they are easy to pack and only one is needed.[28] Thorough washing of the cup and hands helps to avoid introducing new bacteria into the vagina, which may heighten the risk of UTIs and other infections.[29][medical citation needed] Disposable and reusable pads do not demand the same hand hygiene, though reusable pads also require access to water for washing out pads.
A UN spec recommends that cups should not be shared; they should only ever be used by one person.[6]
Insertion[edit]
The vagina is narrowest at the entrance and becomes wider and easier to stretch further in.[31] Menstrual cups are folded or compressed to insert them, and then opened out once inside. The innermost portion of the cup typically goes into the vaginal fornix (the groove around the cervix). Menstrual cups cannot pass through the cervix into the uterus.[32]
The muscles of the pelvic floor, which surround the vaginal entrance, are relaxed to let the cup pass. Involuntarily tensing the vaginal muscles can make it impossible for anything to enter the vagina without causing pain.[33][34] Many initially find insertion difficult, uncomfortable, and even painful, but learn to do it within a few cycles. There is little publicly available research on learning to use menstrual cups which compares types of cup or instructions.[14]
A bell-shaped cup is folded or pinched before being inserted into the vagina.[35] There are various folding techniques for insertion; common folds include the "C" fold, the "7" fold, and the punch-down fold.[36] Once inside, the cup will normally unfold automatically and seal against the vaginal wall.[35] In some cases, the user may need to twist the cup or flex the vaginal muscles to ensure the cup is fully open.[37]
In practice, the rim of a bell-shaped cup generally sits in the vaginal fornix, the ring-shaped hollow around the cervix.[7][33] Some fornixes are much deeper than others.[31] Those with deeper fornixes may use insertion techniques such as inserting the cup partway, opening it before the rim passes the cervix, and then pushing it up into place; or they may press the cup to one side and let it open slowly, the rim slipping over the cervix.[33] If correctly sized and inserted, the cup should not leak or cause any discomfort.[38] The stem should be completely inside the vagina. If it can't be positioned inside, the cup can be removed and the stem trimmed.[35]
Ring-shaped cups (also called menstrual discs or menstrual rings) are inserted differently than bell-shaped cups: by squeezing opposite sides of the rim together until they touch, sliding the inner end of the folded cup to the end of the vaginal canal, and tucking the outer end behind the pubic bone.[34][11] They can be less bulky than a bell-shaped cup, no bulkier than a tampon.[24] Ring-shaped cups have to be placed further in, and it requires more knowledge of anatomy to get them under and around the cervix,[15] not rucked up in front of it.[39] Ring-shaped cups with non-circular rims are designed to be inserted with the widest, deepest part going in first. If they are inserted the wrong way around they may leak.[28][40] If there are stems or other removal aids, they should be on the end inserted last.[34]
If lubricant is used for insertion, it should be water-based, as silicone lubricant can be damaging to the silicone.[41]
Wear[edit]
A bell-shaped cup may protrude far enough to be uncomfortable if it is too long. It may press too firmly against the bladder, causing discomfort, frequent urination, or difficulty urinating, if it is too firm, or the wrong shape.[33] A bell-shaped cup may leak if it is not inserted correctly, and does not pop open completely and seal against the walls of the vagina. Some factors mentioned in association with leakage included menorrhagia, unusual anatomy of the uterus, need for a larger size of menstrual cup, and incorrect placement of the menstrual cup, or that it had filled to capacity.[14] However, a proper seal may continue to contain fluid in the upper vagina even if the cup is full.[citation needed]
If a ring-shaped cup pops out at the outermost edge, either the innermost edge got caught on near side of the cervix rather than tucked into the fornix behind it, or it is too big. In either case it will leak. If it comes loose and starts to slide out when using the toilet, or leaks on exertion (when exercising, coughing, or sneezing), it is too small.[citation needed] Some deliberately choose a ring-shaped cup which will leak when they deliberately bear down on it, but not at any other time.[42][43]
Emptying and removal[edit]
It is possible to deliberately empty a ring-shaped menstrual disc by muscular effort, without removing it (provided it is of a fairly soft material, and the right size). This is done in a suitable location, such as when sitting on a toilet. Bell-shaped cups must be removed to empty them.[42][43]
The cup is emptied after 4–12 hours of use (or when it is full).[18] Leaving the cup in for at least 3–4 hours allows the menstrual fluid to provide some lubrication.[44] Many initially find removal difficult, uncomfortable, and even painful, but learn to do it without problems within a few cycles.[14]
The muscles of the pelvic floor are kept relaxed, to allow the cup to pass out through them.[28] Techniques like squatting, putting a leg up on the toilet seat, spreading the knees, and bearing down on the cup as if giving birth are sometimes used to make removal easier.[44][32][45] Because vaginal tenting can make the cup harder to remove, some manufacturers recommend waiting at least an hour after sex before removal.[46] Slow removal and a firm grip avoid dropping the cup;[45] experience, time and privacy also help.[18]
A bell-shaped cup is removed by reaching up to its stem to find the base. Simply pulling on the stem does not break the seal, and yanking on it can cause pain. To release the seal, the base of the cup is pinched, or a finger is placed alongside the cup.[38][28] The exception is two-part cups with separate stems; those can be pulled out to break the seal.[47] The shape of the (one-part) stem thus has little effect on how easy the cup is to remove, and many people trim the stem right off for comfort.[28] The cup is removed slowly;[38][28] rocking or wriggling it gently may help.[32] Some fold the cup in a "C" fold before removal, to break the seal and reduce the bulk; folding the cup inside the body is generally more difficult than folding it outside.
A cup can be removed over a toilet to catch spills.[48] Removal becomes less messy with practice, and it is possible to consistently remove bell-shaped cup without spilling, by keeping it upright.[49][better source needed] If it is necessary to track the amount of menses produced (e.g., for medical reasons), a bell-shaped cup allows one to do so accurately before emptying.[50]
Ring-shaped menstrual cups are removed by hooking the rim with a finger (from either side), or by pinching it with multiple fingers and pulling. Some ring-shaped cups have a dimple in the bowl, to make it easier to hook the rim from below. Some also have stems, but contrary to bell-shaped cups, these stems attach to the rim of the cup, and can be pulled to break the seal. Others have pull loops that fold flat against the bowl, which can also be pulled to remove.[51] Removing ring-shaped cups is typically done over a toilet in case of spilling; the softer bowl squishes flat during removal, making it very difficult not to spill any blood.[45][51]
If a cup is removed or emptied over a pit latrine, it may fall in and be unretrievable.[52]
When using a urine-diverting dry toilet, menstrual blood can be emptied into the part that receives the feces. If any menstrual blood falls into the funnel for urine, it can be rinsed away with water.[53]
Cleaning[edit]
There is little published or independent research on how to clean menstrual cups. Manufacturers generally provide cleaning instructions, but they differ widely. Manufacturers did not provide any evidence validating or giving a rationale for the various cleaning instructions, as of 2022.[52] A UN specification says that "The cup must be washed frequently in clean, boiling water as per manufacturer's instructions."[6]
A 2022 review stated that "Publicly accessible evidence is needed to create consumer confidence in the recommended cleaning practices... nearly all menstrual cup manufacturers fail to provide any publicly available independent evidence that supports their recommended cleaning practices". The review found no standards or guidelines for menstrual cup cleaning practices, and urged independent research to establish a normative standard.[52]
The most common recommendations are:
- boiling a new cup before using it for the first time, for about five minutes
- when a menstrual cup is removed and emptied, it is generally cleaned before it is reinserted; the most common recommendations were:
- washing with water and a "mild" soap, for preference
- rinsing in water (second choice)
- wiping with a clean, dry wipe such as toilet tissue (third choice)
- boiling or steeping a cup between menstrual cycles for about five minutes.
Most manufacturers recommended using water and soap if readily available. Many counterrecommend scented soaps and soaps made with an excess of oil or fat[52] (in order to create moisturizing soap[54]). Scents and moisturizers are designed to remain as residues on the hands after washing.
In response to the 2022 review, which said there was no published evidence on how well cleaning methods work,[52] a single small in-vitro study (using human blood, but incubation outside the body) compared four cleaning treatments:
- cold water (cup rubbed with fingers under running water for 30 seconds)
- cold water and liquid soap (used instead of the more common bar soap so that the quantity could be more easily measured)
- cold water followed by steeping (putting the cup in a ceramic mug and pouring water over it as soon as the water boiled, then steeping for 5 min with the mug covered by a small plate; after five minutes, the water in the mug was still above 75 Celsius)
- cold water and soap followed by steeping
It did not compare boiling to steeping. All of the methods decreased the bacterial load of the cups, with steeping having a bigger individual effect than soap; when using all three cleaning methods on cups (the fourth treatment), the authors were unable to culture bacteria from them. The authors recommended using as many of the cleaning methods as possible, but using soap only if it can be thoroughly washed off, as soap residue can irritate the vagina. They pointed out the need for in-vivo studies, looking at real health outcomes, and the need for studies on more than the single model of cup they tested.[55]
Some menstrual cups come with cleaning containers; the cup is intended to be steeped in the container with boiling water for five minutes or microwaved in the container with water for 3–5 minutes. Containers are made from a medical-grade silicone or polypropylene.[52]
Some manufacturers sell and recommend proprietary cleaning products.[28][52] These are not considered necessary.[55][28][better source needed]
Method | Before first use | Within cycle | Between cycles | Variations |
---|---|---|---|---|
not cleaning it at all, just reinserting it as-is | has been suggested as a stopgap measure by at least one manufacturer.[56] | |||
rinsing it in water only | 10/24 manufacturers in 2022 recommended this, four of them as an alternative to using soap[52] | rinsing in cold water at least initially to inhibit bloodstains;[46] rinsing it in a sink,[56] or using a water bottle,[56] especially in areas with no running water. Some users carry a bottle of clean water to rinse the cup with when on the road.[52] | ||
washing it in mild soap and water | 17/24 manufacturers in 2022 recommended this[52] 1/24 counterecommended soap, and 1/24 said soap was unnecessary.[52] | 14/17 recommended unscented, oil-free, water-based, nonantibacterial soap. Some counterecommend castile soap, dish soap, and heavy-duty facial cleanser.[52] The scent left by soap is a residue; moisturizing soaps also leave a residue.[citation needed] | ||
washing it in a proprietary menstrual-cup-cleaning solution and water | 9/17 manufacturers in 2022 recommended this as an optional alternative to using soap.[52] | |||
wiping it off, with tissue or another dry wipe, and reinserting it | 8/24 manufacturers in 2022 recommended this.[52] | if using toilet paper, blotting instead of rubbing to stop the paper from disintegrating.[56] | ||
wiping it with a disposable wipe | 1/24 manufacturers recommended wiping with a proprietary soap-based wipe in 2022.[52] | 8/24 manufacturers in 2022 recommended a proprietary wipe.[52] | Some distributors market wipes intended specifically for cleaning menstrual cups; they may contain a variety of active ingredients, including purified water, soap, or denatured alcohol.[52] Non-cup-specific wipes sometimes used include isopropyl alcohol disposable wipe (not the sort with a moisturizer, as that leaves a residue), or wipes such as "feminine wipes" or hypoallergenic baby wipes;[32] some types of wipes have moisturizing lotions, preservatives, or other residues.[citation needed] 3/24 manufacturers counterrecommended cleaning cups with isopropyl alcohol in 2022; 1/24 counterecommended alcohol-based wipes.[52] | |
boiling the cup or steeping, covered, in freshly boiled water (like some types of tea) | In 2022, 18/24 manufacturers recommended this. 7/18 recommended five minutes or less, 7/18 recommended 5–10 minutes, one recommended 10-20 min, and 2/18 recommended over twenty minutes, with one last manufacturer not suggesting a time.[52] | 3/24 manufacturers recommended this in 2022; all offered alternatives[52] | 23/24 manufacturers recommended this or noted it as optional in 2022. 11/23 recommended five minutes or less, 5/23 recommended 5–10 minutes, and 2/23 recommended over twenty minutes, with 5/23 manufacturer not suggesting a time.[52] | Almost all manufacturers recommend boiling before first use. Almost all manufacturers recommend boiling or steeping in boiling water between cycles, as mandatory or as an option, and most users do boil their cups.[52] 2/24 recommended boiling times of no more than five minutes, and 1/24, <10min. Long boiling can damage the cup, and boiling it dry can melt it.[52] [57] Kitchen facilities may lack privacy. Distributors seldom provide a boiling pot; people unable to afford a cup-boiling container sometimes used containers which might leave a harmful residue, like old paint cans.[52] |
steaming the cup in a menstrual-cup steamer[52] | 1/24 manufacturers recommended this in 2022.[52] | 1/24 manufacturers in 2022 recommended this.[52] | Takes 8–10 minutes.[52] Steamer must be cleaned and dried afterwards,[citation needed] USB steamers are not affordable in many lower-and middle-income countries.[52] | |
microwaving | 1/24 recommended microwaving for five minute with water in a proprietary container | 9/24 manufacturers recommended this in 2022.[52] | Some manufacturers recommend, others counterrecommend; one recommended microwaving for five minute with water in a proprietary container, others recommend boiling in water in a microwave. This is not workable in lower-income houses that do not have microwaves.[52] Microwaving in a breast-pump sterilization bag is also sometimes practiced.[citation needed] | |
washing in the dishwasher | 4/24 manufacturers counterrecommended cleaning cups in the dishwasher in 2022.[52] | |||
vinegar solution | 1/24 manufacturers in 2022 recommended boiling in a 1:9 solution.[52] | 1/24 manufacturers in 2022 recommended soaking in vinegar.[52] | 3/24 manufacturers counterrecommended cleaning cups with vinegar in 2022.[52] | |
soaking with a sterilizing tablet (generally sodium dichloroisocyanurate, used for baby bottles and breast pump equipment) | 4/24 manufacturers in 2022 recommended this.[52] | 1/24 manufacturers recommended this in 2022.[52] | 9/24 manufacturers recommended this in 2022.[52] | |
petroleum-based lubricants and essential oils | 6/24 manufacturers counterrecommended using essential oils with cups in 2022; 5/24 countereccomended petroleum lubricants.[52] | |||
"corrosive" or "harsh" cleaning chemicals | 6/24 manufacturers in 2022 counterreccomended this, but none of them were specific about what cleaners were to be avoided. | |||
baking soda | 2/24 counterrecommended using baking soda in 2022; none recommended it.[52] | |||
soaking in hydrogen peroxide solution | Some manufacturers recommend, others (3/24) counterrecommended any sort of bleach in 2022.[52] | |||
soaking in isopropyl alcohol solution | In 2022, one manufacturer recommended soaking thus for 10 minutes.[52] | 2/24 manufacturers in 2022 recommended this.[52] | 3/24 manufacturers counterrecommended cleaning cups with isopropyl alcohol in 2022. | |
ultraviolet light irradiation | Some manufacturers recommend.[52] | |||
ozone generation | Some manufacturers recommend.[52] | |||
a cup with a mechanically superhydrophobic surface | N/A | N/A | N/A | A "microtopographic design that incorporates micron-scale thick lubricant" (polydimethylsiloxane) in a "replenishing slippery surface"; the manufacturer says that week-old bloodstains can be wiped off, and that rinsing in water and wiping are the only cleaning needed.[52][58] |
In practice[edit]
A South African study found that 93% used tap water when cleaning their cups at home, but only 32-44% rinsed their cups with tap water outside the home; when water was not available, many women left their cups in all day.[55]
In situations where clean water is hard to get or in short supply, it may be difficult to clean the cup with water. Reusable alternatives, like washing rags, may take more water.[52] A lack of soap also presents a problem in some developing countries.[59]
Washing a menstrual cup in a sink at a public toilet can pose problems, as the handwashing sinks are often in a public space rather than in the toilet cubicle.[60] Accessible loos generally have sinks that can be reached from the toilet, but they may be needed by people with limited mobility.[56] Some users do not empty cups in public toilets; if they only empty the cup twice a day, every 12 hours, they can wait until they return home.[18][32]
Boiling menstrual cups once a month can also be a problem in developing countries, if there is a lack of water, firewood or other fuel.[61]
A dedicated menstrual-cup-cleaning pot may also be too expensive, and use of kitchen pots socially unacceptable. Alternatives like used paint cans may contain harmful substances.[52] Food cans are used; these hold their temperature better than a ceramic mug for steeping,[55] but there is no data on the safety of tinned or plastic-coated food cans for this use.[62] Mason jars made for home canning are heatproof and designed to be sterilized by boiling; they have been used to steep-sterilize menstrual cups.[63] They have also been used (presumably unsealed) for storage.[64] USB-powered sterilizers and proprietary menstrual cup cleaning solutions are not accessible to poorer users.[52]
Stain removal[edit]
Some suggest scrubbing out grooves with a toothbrush, rag, or cloth,[46] and airholes with an interdental brush.
Stains on any color of the cup can be removed or at least lightened by soaking the cup in diluted hydrogen peroxide,[28] or leaving it out in the sun for a few hours.[65] Some cup makers recommend against the use of hydrogen peroxide.[52][66][67]
Some menstrual cups are sold colorless and translucent, but several brands also offer colored cups.[68] Translucent cups lose their initial appearance faster than colored – they tend to get yellowish stains with use.[18] It can be harder to see whether a dark-coloured cup is clean.[28] The shade of a colored cup may change over time, though stains are often not as obvious on colored cups.
Storage[edit]
Manufacturers typically suggest letting the cup dry out fully and storing it dry in a breathable container, such as the cloth bag usually provided with the cup. Airtight wraps and containers are counterrecommended, especially if the cup is at all damp.[52]
Safety[edit]
Menstrual cups are a safe option for managing menstruation, with risks comparable to or lower than alternatives (with the possible exception of the risk of intrauterine device (IUD) displacement). They are safe in in low-, middle-, and high-income settings.[18]
Using a menstrual cup does not harm the vaginal flora. Studies looked at disruptions of the vaginal flora including excessive growth of yeast, excessive growth of harmful bacteria, excessive growth of Staphylococcus aureus, and other microorganisms; subjects using menstrual cups were not more likely to have these common vaginal problems than subjects using other methods, (cloth or disposable pads, or tampons); in some studies, they were less likely.[18]
Menstrual cups can be used with an IUD, but it isn't clear whether using a menstrual cup increases the risk of IUD expulsion, as of 2023[update].[69] About 6% of all IUD users have an IUD come out unintentionally, most commonly during menstruation. In three studies of expulsion rates in menstrual cup users, the rates were 3.7%, 17.3% and 18.6%. Menstrual cup users differ demographically from the general population of IUD users (for instance, they tend to be younger, and youth independently increases the risk of losing an IUD unintentionally). It has been suggested that when removing a menstrual cup, the user might accidentally pull on the IUD string, or that the suction might pull the IUD out. There is no data on what removal techniques, brands or types of cup might be riskier. Some IUD users have had the strings of their IUD cut quite short as a precaution against accidentally pulling it out while removing a cup.[69]
Rare issues[edit]
The number of menstrual cup users is unknown. This makes it hard to estimate the rate of rarer health problems related to cups. There are few reports, and rare problems are unlikely to turn up in a randomized study.[18]
Serious difficulty removing the cup, requiring professional assistance, is rare but not unknown. A 2019 review found two cases with bell-shaped silicone cups, and one case with an elaborate older model of diaphragm-like cup called a Gynaeseal. There were also 46 reports with a single brand of disposable ring-shaped plastic cup (of about 100 million cups sold); most were reported to the manufacturer.[18]
A 2019 review found three cases in which a malpositioned menstrual cup pressed on a ureter, which blocked the flow of urine from a kidney to the bladder; this caused renal colic (acute pain on the flank and lower back) which went away once the cup was removed. It also found one case of urinary incontinence while using the cup, which cleared up when the cup was removed, and five other urinary complaints.[18]
Most menstrual cups are made of silicone, and silicone allergies are rare. In 2010, there was one report to the FDA of someone with a silicone allergy who had to have reconstructive surgery to the vagina after using a silicone menstrual cup. There were two reports to the FDA of allergic reactions to a disposable plastic cup. A 2017 study in Dharpur, Gujarat, using a silicone cup described as ring-shaped and depicted as bell-shaped, collected two reports of rashes and one report of an allergy.[18]
The 2019 review also found two reports of irritation to the vagina and cervix, neither of which had clinical consequences, and two of severe pain (one on removing a cup for the first time). There were three reports of a vaginal wound from menstrual cup use, but reviewers were not able to review any associated medical records.[18]
One case report noted the development of endometriosis and adenomyosis in one menstrual cup user.[18][70] Endometriosis affects 10–15% of menstruators.[71] An online survey on the topic, with nine respondents, found three people who had used a menstrual cup and developed endometriosis.[72] The U.S. Food and Drug Administration made a public statement that there was insufficient evidence of risk.[73][18]
Toxic shock syndrome[edit]
Toxic shock syndrome (TSS) is a potentially fatal bacterial illness. A 2019 review found the risk of toxic shock syndrome with menstrual cup use to be low, with five cases identified via their literature search (one with an IUD, one with an immunodeficiency).[14] Data from the United States showed rates of TSS to be lower in people using menstrual cups versus high-absorbency tampons.[14] Infection risk is similar or less with menstrual cups compared to pads or tampons.[14]
There is an association between TSS and tampon use, although the exact connection remains unclear.[74] TSS associated with menstrual cup use appears to be very rare,[75][76] probably because menstrual cups are not absorbent, do not irritate the vaginal mucosal tissue, and so do not measurably change the vaginal flora.[24]
The risk of TSS associated with contraceptive cervical caps [77][14] and contraceptive diaphragms[14] is also very low. Like menstrual cups, these products both use mostly medical grade silicone or latex.[78][14]
A widely reported study showed that in vitro, bacteria associated with toxic shock syndrome (TSS) are capable of growing on menstrual cups,[79][80][81] but results from similar studies are conflicting, and results from in-vivo studies do not show cause for concern.[14]
Size, shape, and flexibility[edit]
There are no standards for the measurement or labelling of menstrual cups, and each manufacturer uses their own system.[36] Self-measurement of the vagina and third-party measurement tables are often used to get a good fit.[33][82][9][11]
Capacity affects how often the cup must be emptied. Some prefer to empty the cup only twice a day, morning and evening, to avoid emptying it in public toilets.[18] Flow rates vary. On average, about 30mL of menstrual fluid is lost per month; 10 to 35mL is normal.[83] Menstrual blood loss of more than 80mL per month is considered heavy menstrual bleeding, and grounds for consulting a doctor.[84][85][50]
The stated capacity of menstrual cup is generally measured ex vivo (outside the body). It is the volume of fluid that will fill the cup to just below the airholes, if there are airholes, or just below the rim, if there are none.[50] These volume measurements are generally overestimates of real life capacity, because the cup may be compressed inside the body, and the cervix will often occupy some of the volume of the cup.[28][33][7][40] Ex-vivo capacities for menstrual cups are in the range of tens of milliliters;[6][9] for comparison, a normal-size tampon or pad holds about 5mL when thoroughly soaked.[83]
Bell-shaped cups[edit]
Size category | Length (excluding stem) | Capacity | Rim diameter | Firmness |
---|---|---|---|---|
Small | 40-50mm | 15-25mL | 36-40mm | soft to medium |
Medium | 45-55mm | 20-30mL | 41-44mm | soft to medium |
Large | 48-58mm | 30-40mL | 45-48mm | medium to hard |
Bell-shaped menstrual cups all have a wall thickness of about 2mm. They vary in length, capacity, firmness, and external diameter of the rim. This accommodates variety in anatomy, flow quantity, and personal preferences for firmness.[6]
While vaginal tenting causes the cervix to retract during sexual arousal, it is normally located within centimeters of the vaginal opening; 45-55mmm is a medium height.[82] Cups are available in lengths from about 30-80mm,[9] with 40-60mm lengths being common;[18] menstrual discs are shallower than most cups.[86] Some manufacturers sell several sizes of cup that are all the same length.[87]
Cups must be short enough that the cervix does not push the cup into contact with the vulva, where it may be uncomfortable. If the cervix sits particularly low[6] or is tilted, a shorter cup may needed.[88]
Many bell-shaped cups have stems. The stems can be trimmed to shorten the cup, giving stemmed cups a minimum and maximum length; instructions for trimming are generally included with the cup. Some cups are made in two parts, with a separate stem passing through a hole in the cup; these separate stems, unlike normal one-piece stems, can be pulled to break the seal, and were designed to make removing the cup with low dexterity easier.[89] The UN counterrecommends hollow stems, because solid stems are easier to clean.[6] Moulded text, ridges, bumps, and holes also make a cup harder to clean effectively.[55][28]
Ex vivo, small size cups hold about 15-25 ml, medium size cups 20-30 ml, and large cups 30-40 ml.[6] The maximum capacity for large cups is about 50mL (ring-shaped cups generally hold a bit more than bell-shaped cups).[9] Excessively high-volume cups can be uncomfortably large, so fit is prioritized.[28]
Bell-shaped cups also vary by firmness or flexibility. Some manufacturers make the same cups in a range of firmness levels. A firmer cup pops open more easily after insertion and may hold a more consistent seal against the vaginal wall (preventing leaks), but some people find softer cups more comfortable to insert.[18] The outside diameter of the rim will also affect seal and comfort.[citation needed]
Sizing[edit]
Cervix height is measured by touching the cervix with a fingertip, and using the thumb against the finger to mark the inner edge of the vaginal opening; the distance from the thumbnail to the tip of the finger is the height of the cervix.[82] Cervix height varies slightly over the month, and is usually lowest on the first day of bleeding; minimum height is used for sizing menstrual cups.[82] The cup length is generally taken to be equivalent to the cervix height, but as the cup rim will generally sit in the fornix, some may comfortably take a cup slightly longer than their cervical height.[33] Fornix depth varies, but is usually between 1–5 cm (0.5-2 inches).[31]
Manufacturers do not generally print cup dimensions on the box, but there are third-party tables of dimensions online.[9][90] This forcers buyers to guess whether a cup will fit. A regulatory requirement for quantitative measurements, including a Young's modulus measurement of firmness, has been suggested. Research into what measurements would be most useful for selecting a well-sized cup is also needed.[36]
Most brands sell a smaller and a larger size, but some sell up to five sizes, and differing firmnesses. Sizes are mostly labelled transparently, (e.g. "S", "M", and "L"), but some manufacturers label sizes with ordinal numbers (e.g. "0", "1", and "2"), alphabetic letters (e.g. "A" "B" and "C"), or euphemisms (such as "Petite", "Regular", and "Full fit"). Between one manufacturer's products, volume usually increases with number and position in the alphabet.[11] Mostly, each larger size is slightly larger in all dimensions, but some manufacturers have sizes that differ in only one dimension (length, diameter, or capacity).[91]
These sizes are not consistent between manufacturers.[36][28] Manufacturers typically recommend the smaller size for under-30s who have not given birth vaginally and have a lighter flow, and the larger for everyone else.[92][88] However, there is no medical evidence for sizing based on age or parity.[92]