What actually differentiates these products

Menstrual cups are bell-shaped silicone or rubber devices that sit in the vaginal canal and collect flow. They can hold significantly more than a tampon (up to 30ml versus a tampon's 10–12ml), can be worn for up to 12 hours, and last several years with proper care.

Period discs are flat, flexible discs that sit at the vaginal fornix — higher up, near the cervix — rather than the vaginal canal. The placement difference is meaningful: discs can usually be worn during penetrative sex without the partner feeling it, and they're less likely to cause the pressure or suction sensation some cup users report. They're typically single-use, though reusable silicone disc options now exist.

Period underwear has an absorbent layer sewn into the gusset. It works externally, like a wearable pad, and is designed for light to moderate days or as a backup. The 2024 PFAS discovery (discussed below) changed how people should shop for it.

99%
reduction in menstrual waste plastic when switching from disposable pads and tampons to a reusable cup — per lifecycle analysis data
12 hrs
maximum recommended wear time for a menstrual cup — keeping it shorter reduces any infection risk, though TSS is rare with cups
2–10 yrs
lifespan of a quality silicone menstrual cup with proper cleaning — making the cost per use substantially lower than disposables

The PFAS issue in period underwear

In 2023 and 2024, independent testing found elevated markers of PFAS (per- and polyfluoroalkyl substances) in the absorbent layers of multiple period underwear brands. PFAS are often used to make textiles water-resistant and don't break down in the body or the environment.

Not all brands tested positive, and some that did have since reformulated. But the testing gap between brands was significant, and there's no consistent labeling requirement in the US. The practical guidance is to look for third-party PFAS testing certifications (OEKO-TEX STANDARD 100 or GOTS) or choose brands that publish their own testing data. Avoiding products that don't disclose absorbent layer composition is reasonable until regulation catches up.

Research Evidence

A systematic review in The Lancet Public Health (updated 2023) reviewed 43 studies covering menstrual cup use across multiple countries and concluded cups are safe, effective, and associated with high user satisfaction after an initial learning curve. Adverse events were rare and most commonly involved difficulty inserting or removing the cup — not infection or injury. The review noted a lack of comparative data against period discs specifically.

Which is right for you? The honest answer

If you have never used an internal period product, the disc may be easier to start with than the cup — less learning curve with the fold and positioning. For heavy flow days, a cup or disc plus period underwear as backup is a genuinely comfortable combination used by many women.

If you have a tilted uterus or pelvic floor issues, a cup may sit uncomfortably. Some women with fibroids or IUDs should confirm cup safety with their gynecologist first, as rare reports of IUD displacement exist — though current evidence suggests the risk is low with proper insertion technique.

What to know before you switch

  • ✓
    Give yourself two to three cycles to get comfortable with a cup. Most users who quit do so in the first month. Fit and fold technique take practice — the learning curve is real but short.
  • ✓
    For period underwear, look for third-party PFAS certification before buying. Brands that have published independent testing results are the safer choice right now.
  • ✓
    Tell your OB-GYN if you have an IUD. While displacement is rare, it's worth confirming that the suction from cup removal is managed correctly — your doctor can walk you through the technique.
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OB-GYN's Note

Reusable period products are well-supported by evidence and most women can use them safely. The most common clinical issue I see is incorrect cup sizing — most brands offer size options and the guidance on their packaging is usually helpful. If you experience significant cramping with a cup, it may be sitting too high and creating suction on the cervix. Repositioning usually resolves it immediately.

Medical Disclaimer: This article is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Sources

  1. van Eijk AM, et al. Menstrual cup use, leakage, acceptability, safety, and availability: a systematic review and meta-analysis. Lancet Public Health. (2019, updated 2023). The Lancet
  2. Menstrual Technology Innovations and Heavy Menstrual Bleeding. (2023). PMC. PMC10026971
  3. Reusable Period Products: PFAS Testing Findings. Saalt blog citing independent lab results. (2024). saalt.com
  4. HealthPartners. Feminine products: Pros and cons of each type. healthpartners.com
  5. Why More Women Are Switching to Reusable Menstrual Products. US News. (2025). usnews.com