Menstrual products: culprits or bystanders in endometriosis and adenomyosis pathogenesis?

Products that may reduce menstrual flow from the endometrial cavity to the vagina (i.e. tampons and menstrual cups) could facilitate retrograde menstruation and the spillage of blood into the myometrium, two mechanisms which could be major determinants in endometriosis and adenomyosis pathogenesis. The aim of this narrative review is to summarize the evidence regarding the mechanical role menstrual products may have in the pathogenesis of these two conditions. Evidence in this regard is inconclusive. While Darrow and colleagues observed that 14 or more years of tampon use were associated with endometriosis (OR 3.6; 95% CI, 1.04-13.5); in Meaddough and colleagues' retrospective study, the percentage of women using pads only was significantly higher among those with endometriosis than among those without the condition (31% vs 22%). Three further groups failed to find an association between endometriosis/adenomyosis and any type of menstrual product. The only case that may be considered as a sort of proof-of-concept of the association between products potentially reducing anterograde menstrual flow and endometriosis was reported by Spechler and colleagues, who described the case of a 41 year-old who developed endometriosis after having used a menstrual cup on a regular basis. However, the number of studies on the subject is scarce, study populations are exiguous and a greater attention to temporality of endometriosis onset in relation to when women started habitually using a specific menstrual product is needed. Confounding variables including type and quantity of endocrine disruptors contained in menstrual products should also be addressed. At the present moment, no recommendation can be provided on the safety of one type of menstrual product compared to another.