Menstrual cup use, leakage, acceptability, safety, and availability: a systematic review and meta-analysis

1Girls and women need effective, safe, and affordable menstrual products. Globally, an estimated 1·9 billion women—around 26% of the population—were of menstruating age in 2017, spending on average 65 days in the year dealing with menstrual blood flow. Menstruation is a normal body function and a sign of reproductive health. Few solutions are available to manage menstruation; additionally, ignorance, prejudice, costs, and safety fears can impede girls and women from testing the full range of products available. A lack of affordable and effective menstrual products can result in leakage and chaffing in menstruating girls and women and can affect their health., Use of poor-quality materials has been shown to predispose women to an increased risk of urogenital infections including bacterial vaginosis.,, In some situations, mostly researched in low-income and middle-income countries, menstruation can affect girls' schooling, make women and girls a target of sexual violence or coercion,, and affect employment and work experiences of women., In low-income and middle-income countries, a lack of water, sanitation, and hygiene, inadequate education, and poor disposal facilities, raise public health concerns, particularly among schoolgirls., In several countries, the number of policy-led initiatives and donations to provide menstrual products have increased—eg, to keep girls in school. To allow such organisations to make informed decisions, information is needed on the full range of menstrual products.

2Evidence before this studyA lack of affordable and effective menstrual products can result in leakage and chaffing in menstruating girls and women and can affect their health and education. The number of programmes that provide menstrual products to assist women and girls has increased. The menstrual cup, a receptacle used to collect menstrual blood flow, has received little attention, which in part might reflect concerns about insertable products as either culturally unacceptable or because of previous public health alerts associated with highly absorbent tampons (eg, toxic-shock syndrome). Information about leakage, acceptability, and safety of menstrual cups is needed to support organisations to make informed decisions and provide more comprehensive menstrual health education for girls and women. We searched PubMed, Cochrane Library, Web of Science, Popline, Cinahl, Global Health database, Emerald, Google Scholar, Science.gov, and WorldWideScience from database inception on Nov 24, 2018, for publications in English using the keywords (“Menstrual Cup”) AND “Review” to determine if a review of menstrual cups was available with information on leakage, acceptability, and safety. No review was identified, but a literature review on menstrual management in emergency contexts noted a lack of empirical evidence examining the introduction and testing of menstrual cups in humanitarian settings.Added value of this studyTo our knowledge, this is the first systematic review and meta-analysis examining girls' and women's experiences of menstrual cups, aggregating outcomes from 43 studies and 3319 participants who were asked about their use or willingness to use menstrual cups. We provide information on leakage compared with other products, a listing of known adverse events, and quantitative and qualitative information on acceptability in both high-income countries and low-income and middle-income countries. We also assessed availability and prices of menstrual cups. Serious adverse events were not common, with five reported cases of toxic-shock syndrome. However, the number of menstrual cup users is unknown, so comparisons of risk of toxic-shock syndrome between menstrual cups, tampons, or the intravaginal diaphragm cannot be made. Although menstrual cups are manufactured and available globally, they are not commonly mentioned on websites offering educational materials on puberty for girls.Implications of all the available evidenceMenstrual cups seem to be an effective and safe alternative to other menstrual products. Information on menstrual cups should be provided in puberty education materials. Policy makers and programmes can consider this product as an option in menstrual health programmes. Further research globally can provide more information on acceptability and is needed to monitor adverse events and assess best practice to shorten the familiarisation phase required for safe and effective use, and on cost-effectiveness and environmental effects.

3Evidence before this study

4A lack of affordable and effective menstrual products can result in leakage and chaffing in menstruating girls and women and can affect their health and education. The number of programmes that provide menstrual products to assist women and girls has increased. The menstrual cup, a receptacle used to collect menstrual blood flow, has received little attention, which in part might reflect concerns about insertable products as either culturally unacceptable or because of previous public health alerts associated with highly absorbent tampons (eg, toxic-shock syndrome). Information about leakage, acceptability, and safety of menstrual cups is needed to support organisations to make informed decisions and provide more comprehensive menstrual health education for girls and women. We searched PubMed, Cochrane Library, Web of Science, Popline, Cinahl, Global Health database, Emerald, Google Scholar, Science.gov, and WorldWideScience from database inception on Nov 24, 2018, for publications in English using the keywords (“Menstrual Cup”) AND “Review” to determine if a review of menstrual cups was available with information on leakage, acceptability, and safety. No review was identified, but a literature review on menstrual management in emergency contexts noted a lack of empirical evidence examining the introduction and testing of menstrual cups in humanitarian settings.

5Added value of this study

6To our knowledge, this is the first systematic review and meta-analysis examining girls' and women's experiences of menstrual cups, aggregating outcomes from 43 studies and 3319 participants who were asked about their use or willingness to use menstrual cups. We provide information on leakage compared with other products, a listing of known adverse events, and quantitative and qualitative information on acceptability in both high-income countries and low-income and middle-income countries. We also assessed availability and prices of menstrual cups. Serious adverse events were not common, with five reported cases of toxic-shock syndrome. However, the number of menstrual cup users is unknown, so comparisons of risk of toxic-shock syndrome between menstrual cups, tampons, or the intravaginal diaphragm cannot be made. Although menstrual cups are manufactured and available globally, they are not commonly mentioned on websites offering educational materials on puberty for girls.

7Implications of all the available evidence

8Menstrual cups seem to be an effective and safe alternative to other menstrual products. Information on menstrual cups should be provided in puberty education materials. Policy makers and programmes can consider this product as an option in menstrual health programmes. Further research globally can provide more information on acceptability and is needed to monitor adverse events and assess best practice to shorten the familiarisation phase required for safe and effective use, and on cost-effectiveness and environmental effects.

9The menstrual cup is not commonly known, despite its long history (appendix p 2). Like tampons, menstrual cups are inserted into the vagina, but the blood is collected in the receptacle, which can hold 10–38 mL of blood. The menstrual cup should be emptied every 4–12 h, depending on menstrual flow and type of cup. Two types of cup are available, a vaginal cup, which is generally bell-shaped and placed in the vagina, and a cervical cup, which, like a diaphragm for contraception, is placed around the cervix high in the vagina. Menstrual cups are made of medical-grade silicone, rubber, latex, or elastomer and can last up to 10 years; disposable single-use menstrual cups also exist.

10We aimed to summarise current knowledge about leakage, safety, and acceptability of menstrual cups and compared, when available, with other menstrual products. We compiled information on global availability and costs of menstrual cups, did preliminary estimates on costs and waste savings, and examined online guidance materials on menarche in selected regions of the world for reference to menstrual cup as a product option.

11In this systematic review and meta-analysis, we searched PubMed, Cochrane Library, Web of Science, Popline, Cinahl, Global Health database, Emerald, Google Scholar, Science.gov, and WorldWideScience for material in English from the inception of the database until May 14, 2019, using the keywords (“menstrual” AND “cup”) OR (“menses” AND “cup”) OR (“menstruation” AND “cup”) OR (“vaginal” AND “cup”). We also screened the Manufacturer and User Facility Device Experience (MAUDE) database from the US Food and Drug Administration (FDA) for events related to menstrual cups (10-year limit, last search done on May 28, 2019). For information on costs and availability, we screened websites of menstrual cup manufacturers using different web listings and web searches and consulted experts (full lists are in the appendix [pp 35–39]).

12To ensure we covered a broad range of the available literature, we searched the reference lists of relevant studies, websites of pertinent professional bodies (eg, FDA), non-governmental organisations, and grey literature (eg, reports or conference abstracts), and we contacted experts in the field to recommend relevant reports. For information on costs and availability, our search included individually going through every list of menstrual cup brands we could find and searching where they were being sold (via web lists, Google searches, Pinterest boards, Facebook pages, and experts working in countries where cups appeared to be unavailable to confirm).

13Study eligibility, data extraction, and risk-of-bias assessment were done independently by two reviewers (AMvE and ML for quantitative and LM and GZ for qualitative studies), and conflicts were resolved via discussion until an agreement was reached. To be eligible for inclusion, the material needed to have information on leakage, acceptability, or safety of menstrual cups. Quantitative, qualitative, or mixed design studies were included. Animal studies, and studies using menstrual cups to collect vaginal fluids without participants' reported experiences during menstruation were ineligible.

14The main outcome of interest was menstrual blood leakage when using the menstrual cup. Additional outcomes of interest were acceptability of use of menstrual cups, difficulty with insertion or removal, comfort of wearing, and intention to use in future. Safety outcomes of interest included serious adverse events, such as toxic shock syndrome; vaginal abrasions and effects on vaginal microflora (eg, vaginal discharge, infections); effects on the reproductive, digestive, or urinary tract; and safety in poor sanitary conditions. Other safety issues we identified only during our review were documented, and all material was re-reviewed to ensure completeness of the safety assessment.

15Data were manually extracted from studies using spreadsheets. If the same results from the same study were presented in several reports, we used data from the report with the largest sample size. For quality and bias assessments, we used the Cochrane tool for trials, an adaptation of the Newcastle-Ottawa tool (appendix p 5) for observational studies,, and the Critical Appraisal Skills Programme tool for qualitative studies.

16We tabulated our findings as a narrative synthesis. If trials or studies presented sufficiently homogeneous data in terms of design, we pooled results as proportions using meta-analyses and a random-effects model with heterogeneity quantified using the I2 statistic (appendix p 3). We examined the following sources of heterogeneity if sufficient data were available using subgroup analysis: setting of the study (high-income vs low-income and middle-income countries), study population (adult women vs adolescents), year of study (study conducted before or after 2000), type of menstrual cup used (cervical vs vaginal cup), and duration of menstrual cup use. We assessed publication and small-study bias by visual inspection of funnel plots and Egger's test. We integrated the quantitative and qualitative analyses for the acceptability of use of menstrual cups.

17For estimations on costs of disposable pads and tampons, we explored prices for commonly used products in six countries (the USA, the UK, India, Spain, China, and Canada) and calculated average costs per product. Extrapolating information on content and weight of menstrual products, we estimated waste and costs for a range of 9–25 units per product per month and compared these with consistent use of one menstrual cup for 10 years. Additional information on methods used to assess menstrual cup information, availability and prices, qualitative studies, and costs and waste, and additional information on data extraction are in the appendix (pp 3–5).

18We did a sensitivity analysis of low versus moderate-to-good quality studies, as determined by the quality assessment and assessed small-study effect using funnel plots and the Egger's test. We used two-tailed p values of less than 0·05 to indicate statistical significance. We did statistical analyses using Metaprop, Stata version 14.2.2. This systematic review is registered on PROSPERO, number CRD42016047845.

19The funders had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author had full access to all data in the study and had final responsibility to submit for publication.

20Of 436 unique records identified (appendix p 6), 59 were identified as relevant (figure 1), and 43 studies were included in our analysis (table 1). In these 43 studies, 3319 participants used or were asked about the menstrual cup.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Seven studies were completed among schoolgirls (ie, aged 12–19 years) in low-income and middle-income countries (647 [19·5%] participants).,,,,, Three studies were done in the early 1960s, six in the late 1980s, and 26 in 2009–18. 15 studies were from low-income and middle-income countries. Most studies reported on vaginal cups (27 [63%] vaginal cups, five [12%] cervical cups, and 11 [25%] mixed types of cups or unknown) and 35 (81%) were journal articles. Although some studies did not report the type or brand of menstrual cup used, at least seven described menstrual cups that are no longer available (Tassette, Tassaway, and Gynaeseal). The quality of quantitative studies was low, with only two that were of moderate-to-high quality (table 1; appendix pp 7–8). Many studies did not clearly identify where their participants were from, or participants were not representative of the community. Only six studies, all from low-income and middle-income countries, provided qualitative information (appendix p 10).

21With regard to leakage, only four studies (n=293) made direct comparisons between menstrual cups and usual products. The outcomes in each of these studies were different, but leakage between products was similar in three studies and significantly less among menstrual cups for one study (figure 2). In studies that assessed menstrual cups that are still available, the proportion of leakage among the participants who reported use of the menstrual cup was 2–31% for a wide range of definitions, as shown in figure 2. Some factors mentioned in association with leakage by study authors 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.,

22When looking at safety, use of the menstrual cup was not associated with abnormalities in the vagina or cervix in three studies with vaginal examinations (n=370; table 2).,, Three users reported vaginal wounds in case reports, which could not be confirmed with medical records. In one case report, severe pain on removal was self-reported and in another case report severe pain was self-reported when wearing the menstrual cup, and two participants in two different cohort studies reported vaginal or cervical irritation without clinical consequences., Three adverse events that were reported in one cohort study and three case reports were possibly related to an allergy; one case of silicone allergy necessitated reconstructive vaginal surgery.,, Difficulty with removal that required professional assistance—an adverse event we did not anticipate—was reported 47 times for cervical cups (one participant from a cohort study, and 46 case reports) and twice for vaginal cups (both case reports).,,,

23We found no increased infection risk (reproductive tract or systemic infection) associated with use of a menstrual cup among European,, North American, and African women and girls,, compared with other menstrual products (table 2). A decrease in candidiasis was reported with use of the menstrual cup in two of four studies that investigated this infection; one study found no candidiasis infections at follow-up in 18 participants, and the other, a randomised feasibility pilot among schoolgirls (aged 14–16 years) in Kenya comparing menstrual cups, sanitary pads, and usual practice (cloths, pads, tissue, or other makeshift materials), showed no difference in the prevalence of candidiasis by study group (menstrual cup 11 [8%] of 143, pads 19 [10%] of 200, and usual practice 13 [9%] of 156; menstrual cup vs pads p=0·68 and menstrual cup vs usual practice p=0·87; table 2).,,, One study reported lower prevalence of bacterial infections among users of the menstrual cup than among users of tampons or pads (not further specified), and a randomised pilot study in Kenya reported lower prevalence of bacterial vaginosis among users of the menstrual cup than users of pads and usual practice enrolled for 9 months or longer (menstrual cup 13 [13%] of 101, pads 29 [20%] of 143, usual practice 20 [19%] of 104; menstrual cup vs pads p=0·018 and menstrual cup vs usual practice p=0·074; table 2)., Toxic shock syndrome was identified in five case reports;,, microbiological confirmation was available with cultures from menstrual cup and blood showing streptococcus for one case. In two participants from two case reports, concomitant conditions were present (intrauterine device [IUD] in situ; an immunodeficiency disease)., A potential additional case of toxic shock syndrome was identified in a web blog (appendix pp 43–44): we could not determine whether this case has separately been reported in the MAUDE system or in a case report and thus it has been left out of our analysis. The prevalence of vaginal Staphylococcus aureus was examined among Kenyan schoolgirls participating in a randomised pilot study;, no difference was seen between menstrual cup, pads, and usual practice groups. No expression of toxic shock syndrome toxin 1 (TSST-1) was found in S aureus positive samples from menstrual cup users in this study. In-vitro studies of production of TSST-1 in the presence of menstrual cup material showed conflicting results (table 2).,

24An initial case report of a menstrual cup user about dislodgement of her IUD during use of a menstrual cup was followed by a case series of seven women who reported dislodgement of an IUD during removal of the menstrual cup between 1 week and 13 months of IUD insertion., A retrospective chart survey did not find an increased risk for IUD expulsion within 6–8 weeks after insertion among menstrual cup users (five [4%] of 135), compared with tampons users (11 [2%] of 469) or pad users (seven [4%] of 169).

25One case-report suggested use of a menstrual cup might have been associated with the development of endometriosis; however, this hypothesis was not considered plausible by the regulatory authority and we did not identify any further reports on this possible association. We found three case reports,, of hydronephrosis and one of incontinence when using the menstrual cup; however, symptoms disappeared after menstrual cup removal (table 2).,, Other uses of menstrual cups—eg, as a contraceptive or temporary fistula control—are in the appendix (p 9)

26When assessing uptake and acceptability, all six relevant qualitative studies were from low-income and middle-income countries (appendix pp 10–13),,,,,,, whereas 20 studies with quantitative information on uptake and acceptability were from low-income and middle-income countries and high-income countries (appendix pp 14–22).,,,,,,,,,,,,,,,,,,, In low-income and middle-income countries, usual products for menstruation included cloths, disposable pads, cotton wool, tissue paper, or other items, and leakage and chaffing is a common concern.,,,, All studies that assessed use of menstrual cups used some form of education and training on the menstrual cup. Girls and women expressed initial concerns in qualitative studies, noting the size of the menstrual cup. Many were concerned it could cause pain (and noted it often did so at first) or worried about reproductive harms (eg, infertility). In quantitative studies, 3% (pooled estimate: n=1251, 95% CI 1–6%, 11 studies; I=79·3%) of participants reported they could not insert the menstrual cup and 11% (n=1190, 95% CI 3–23%, ten studies; I=96·4%) reported discontinuation related to the menstrual cup (table 3). Pain on insertion was reported for ten (9%) of 106 menstrual cup users versus none of 104 using their usual method at 3 months of follow-up in a South African crossover trial (p value not reported). Initial discomfort on insertion was reported by 20% of participants (pooled estimate: n=1061, 95% CI 12–30%, 17 studies; I=92·3%). All qualitative studies described user familiarisation with the menstrual cup over time, with practice, peer support, and training being key to success.,,,,, Longitudinal quantitative studies in low-income and middle-income countries showed a learning curve of 2–5 months (appendix p 22); colour change of the menstrual cup as an objective measure suggested use increased throughout the first year among Kenyan schoolgirls. A Nepalese study noted that self-reported increased use 2 months after distribution was associated with the presence of friends who successfully used the menstrual cup. In India and Tanzania, the uptake of menstrual cups was significantly slower than uptake of pads (appendix p 24)., In 15 studies with relevant information, 73% (pooled estimate: n=1144, 95% CI 59–84; I=96%) of participants reported willingness to continue use of the menstrual cup after the study (figure 3). All qualitative and some quantitative studies reported a positive effect of use of the menstrual cup on participants' lives, decreased stress concerning staining and leakage, and improvements in mobility.,, Challenges described included difficulties with cleaning and storage of the menstrual cup in low-income and middle-income countries., Other challenges were associated with emptying the menstrual cup in school or public toilets,,, which was also reported by participants in high-income countries. Menstrual cups were associated with a decrease in the average number of changes per cycle in a UK study compared with tampons or sanitary pads. Three qualitative studies implied that school attendance, concentration, and performance improved after participants were given a menstrual cup.,, No measured difference in school absence or test results between products were reported (appendix p 24).,, A study in Nepal noted a significant decrease in time spent doing laundry for menstrual cup users compared with those using usual practice.

27An economic advantage of a menstrual cup emerged in qualitative studies, with participants (and families) citing monthly cost savings from not needing to purchase pads or soap for laundry. Two qualitative studies included quotes from participants showing that menstrual cups might decrease the need for transactional sex to purchase pads., This finding might be corroborated by results from a randomised controlled study among schoolgirls (aged 14–16 years) in rural western Kenya that noted a significantly lower prevalence of sexually transmitted infections among participants who were provided by the study with either menstrual cups or disposable pads versus controls (ie, using usual practice), citing lower exposure to transactional sex as a probable reason (table 2; appendix p 24).

28A study in schoolgirls in Kenya (aged 14–16 years) in an area with poor water and sanitation reported dropping of menstrual products during changing of cloths or disposable pads, or emptying of the cup. The frequency was similar for menstrual cups and sanitary pads. Factors involved included young age, and lack of time and privacy. Dropping of the menstrual cup decreased with increasing experience (approximately 23% in the first 3 months and 10% at or after 12 months). This dropping was associated with Escherichia coli isolated in cultures from swabs of menstrual cups, which was higher in new users than in experienced users (table 2). The proportion of girls who washed their hands before changing of the menstrual cup, by verbal self-report, was 95% (204 of 215) in a Kenyan report, 70% (16 of 23) in a Ugandan report, and 94% (15 of 16) in a study in a refugee camp. When toilets have a lack of water, some participants reported carrying a bottle of water for when they emptied their menstrual cup. Others said they had to empty the menstrual cup only twice a day, so they could avoid emptying in public places. In two studies, women reported that use of menstrual cups saved water because of less leaking and washing of cloths., Privacy was mainly mentioned as a problem when boiling (ie, cleaning) or storing menstrual cups.,

29We identified considerable heterogeneity in outcomes of acceptability of menstrual cups in the pooled meta-analyses (table 3). Subgroup analyses by study quality (low vs moderate-to-good) for outcomes examined did not show significant differences for the outcomes examined, but the sample size for moderate-to-good quality studies was small (appendix p 23). Smaller studies sometimes show different, often larger, treatment effects than large studies (ie, small-study effect); except for the outcome of “could not insert cup” (p=0·041), we did not find evidence for the presence of small-study effects (appendix p 23).

30In the assessment of visibility in three studies in high-income countries, only 11–33% of the women interviewed (n=375) were aware of menstrual cups (appendix p 25).,, On 69 websites with educational materials on puberty and menarche from 27 countries, disposable pads were mentioned as an option by 53 (77%), tampons by 45 (65%), menstrual cups by 21 (30%), and reusable pads by 15 (22%; appendix pp 26–28). In the assessment of costs and availability, we identified 199 brands of menstrual cups, and availability in 99 countries with prices ranging US$0·72–46·72 (median 23·3 [IQR 16·54–29·20], from 145 brands with prices available; appendix pp 29–39).

31When considering financial and environment costs, using accumulated estimates over 10 years, purchase costs and waste from consistent use of a menstrual cup (vaginal cup) would be a small fraction of the purchase costs and waste of pads or tampons—eg, if compared with using 12 pads per period, use of a menstrual cup would comprise 5% of the purchase costs and 0·4% of the plastic waste, and compared with 12 tampons per period, use of a menstrual cup would comprise 7% of the purchase costs and 6% of the plastic waste (appendix pp 40–42).

32Women, girls, and transgender people require hygienic menstrual products monthly to live healthy and productive lives. In this systematic review and meta-analysis, we assessed the menstrual cup, combining information from medical and grey literature to inform choice and strengthen the evidence base for programmes supporting menstrual health, such as for schoolgirls in low-income and middle-income countries or among refugees. Leakage was similar or less when using the menstrual cup than when using disposable pads and tampons. The adoption of a menstrual cup required a familiarisation phase and peer support seemed to be important for uptake in low-income and middle-income countries. Challenges in resource constrained settings (eg, lack of sanitation, hygiene, and privacy) did not stop women from using the cup. Around 70% of participants in 13 studies declared wanting to continue use. We identified several incidental case reports of vaginal damage, toxic shock syndrome, or urinary tract complaints after menstrual cup use, and difficulty retrieving the menstrual cup was also reported. Use of menstrual cups has been described as a factor for IUD dislodgement. Menstrual cups were infrequently mentioned in online educational materials on puberty and menstruation for adolescent girls; the lack of information appears to be global. Brands of menstrual cups were identified in 99 countries with a wide range in prices with a median of US$23·30.

33In studies that examined the vagina and cervix during follow-up, no mechanical harm was evident from use of a menstrual cup.,, Infection risk did not appear to increase with use of a menstrual cup, and compared with pads and tampons, some studies indicated a decreased infection risk.,, A study in Kenya that detected lower bacterial vaginosis in users of a menstrual cup than in those who used sanitary pads postulated that the inert material of the menstrual cup might assist in maintaining a healthy vaginal pH and microbiome. Reported pain might relate to variations in the pelvic anatomy or wrong positioning of the menstrual cup leading to internal pressure. These factors could account for case reports of hydronephrosis or urinary incontinence. Allergies to the materials used in menstrual cups are not common, but women should be aware of the possibility and keep this in mind when starting use. However, for women who start using a menstrual cup, discrimination between discomfort as part of the normal learning curve and pathology might be difficult. Laboratory studies have shown contradicting results on the possibility of development of TSST-1 in the presence of menstrual cups,,, but clinical data in humans using cups have so far not shown reason for concern. The reported risk of toxic shock syndrome with use of a menstrual cup seems low, with five cases identified via our literature search. Although aggregated data on the number of menstrual cups sold or used is unavailable, we anticipate the number of girls and women using the 199 different brands globally is likely to be in the thousands. In the USA, the incidence of all types of toxic shock syndrome was around 0·8–3·4 per 100 000 population, whereas menstrual toxic shock syndrome was reported in 6–12 per 100 000 users of high-absorbency tampons in 1980. Similarly, among women using female barrier contraceptives, which also use medical-grade silicone or latex products, toxic shock syndrome is low (approximately 2·25 cases per 100 000 users per year).

34The combination of an IUD and use of a menstrual cup might need further study. Women with IUDs might need to consider an alternative option for either family planning or menstrual flow. Given the few reports on menstrual cups thus far, we cannot yet exclude other issues with the use of menstrual cups. Few studies directly compared menstrual cups and other menstrual products or materials; however, data do not suggest the menstrual cup is less effective than other sanitary products. Menstrual cups can collect more blood than tampons or sanitary pads and have been adopted by women with menorrhagia. The studies we reviewed report that under challenging conditions (eg, with little water or privacy), menstrual cups can be used. Alternatives to menstrual cups and disposable sanitary pads include reusable pads, so far assessed in few studies.,,, In Uganda, privacy to dry these pads was a challenge, suggesting additional packs would be needed to ensure effective laundering.

35Our study had several limitations. We used leakage as a primary outcome; however, the outcomes identified in the reports and studies reviewed varied by different timepoints and designs, prohibiting combination of results when directly comparing menstrual cups with another item. The quality of studies was a limitation, with only three assessed to be of good quality, which will potentially have contributed to bias in the meta-analysis. Some data were from older studies when reporting requirements were less stringent or with menstrual cups that are no longer available, from reports not published in peer-reviewed journals, and from studies using the menstrual cup to assess other topics (eg, understanding how uncertainty barriers can be overcome in economics, use of reusable menstrual products because of environmental concerns, the association between self-objectification and attitudes toward an alternative menstrual product). Recruitment in observational studies was not representative or clear. Studies mostly depended on self-reporting, which might have overestimated use of the menstrual cup. One study comparing self-reporting against a conservative but objective measure of the colour change of the menstrual cup found uptake of use of the menstrual cup was slower than self-reported—eg, by 4 months, 75% of recipients stated they had started using the cup, whereas only by 10 months did 75% of menstrual cups show appropriate colour change. The number of countries where menstrual cups were available might be underestimated because producers of menstrual cups in low-income and middle-income countries might not always have websites. Our search was in English, and thus lacked information from many countries, such as Russia or China. The heterogeneity for the pooled prevalence was high in the meta-analyses (I≥74%), indicating inconsistency in outcomes across studies. Given the high variability in study design, study period, study population, and products examined, this heterogeneity might not be unexpected. What proportion of adverse events are under-reported is unknown; we did not identify many adverse events (one case of toxic shock syndrome) when exploring the internet (appendix pp 43–44). The MAUDE database only allows searches for the past 10 years. Our cost and waste estimates are illustrative and do not account for the combined use of menstrual products during a period or inflation and production costs.

36This systematic review suggests that menstrual cups can be an acceptable and safe option for menstrual hygiene in high-income, low-income, and middle-income countries but are not well known. Our findings can inform policy makers and programmes that menstrual cups are an alternative to disposable sanitary products, even where water and sanitation facilities are poor. However, provision of information, training, and follow-up on correct use might be needed. Further studies are needed on cost-effectiveness and environmental impact comparing different menstrual products, and to examine facilitators for use of menstrual cups, with monitoring systems in place to document any adverse outcomes.