Menstrual Cups Do Not Cause Endometritis
Based on current evidence, menstrual cups do not cause endometritis. There is no documented association between menstrual cup use and endometritis in the medical literature.
Understanding the Distinction
It's critical to distinguish between endometritis (infection/inflammation of the endometrial lining) and endometriosis (ectopic endometrial tissue). The evidence addresses different concerns:
What We Know About Menstrual Cups and Infections
- No endometritis cases reported: Large systematic reviews examining menstrual cup safety have not identified endometritis as a complication 1, 2
- Vaginal flora remains unaffected: Studies demonstrate that menstrual cup use shows no adverse effects on vaginal microbiota (507 women across 4 studies) 1
- Rare infectious complications: Only 5 cases of toxic shock syndrome have been reported globally with menstrual cup use 1, 2
The Theoretical Concern About Retrograde Flow
While older guidelines note that uterine instrumentation can facilitate upward bacterial spread 3, and recent theoretical discussions suggest menstrual products might affect retrograde menstruation 4, the actual clinical evidence does not support menstrual cups causing endometritis.
Safety Profile from Systematic Reviews
The 2019 Lancet systematic review (43 studies, 3,319 participants) found 1:
- 73% of users wished to continue cup use
- Adverse events were rare and primarily mechanical (removal difficulties, IUD dislodgement)
- No pattern of ascending uterine infections
A 2023 study did identify a potential association with fungal infections (not endometritis) in cup users, though this required further validation 5.
Clinical Bottom Line
Menstrual cups are safe regarding endometritis risk. The pathogenesis of endometritis involves sexually transmitted organisms (Chlamydia, Gonorrhea) or polymicrobial ascending infection from bacterial vaginosis 3—mechanisms unrelated to menstrual cup use. The cup itself does not introduce pathogens or create the conditions necessary for endometritis development.
If a patient using a menstrual cup develops symptoms of endometritis (pelvic pain, abnormal discharge, fever), investigate the standard causes: STIs, bacterial vaginosis, or recent uterine instrumentation—not the menstrual cup itself.