Lots of people tweeting about menstrual cups, which is great!! I am pro cup. I see lots of sources recommending various size fitting techniques, but I can't find any study on sizing a cup. Most studies just provide one size and satisfaction is high. Which is great!!! 1/6

Can anyone point me to any clinical trial that actually uses these sizing guides and compares outcomes? Some recommend different sizes before and after age 30, but there is no magical vaginal-size-change at that point in time. 2/6

I was raised on the idea that women needed to be fit for a diaphragm, but a clinical trial showed 98% of women could use a single size diaphragm. SO wondering if maybe there is cup size dogma? 3/6 https://pubmed.ncbi.nlm.nih.gov/25751199/?from_term=diphragm+size+fit&from_filter=pubt.clinicaltrial&from_filter=species.humans&from_exact_term=diaphragm+size+fit&from_pos=1

With pessaries we start with a rough idea of vaginal width based on exam and then try different sizes based on how that feels. We have the patient walk around for comfort (and to make sure it doesn't fall out) and to empty their bladder. It's very trial and error. 4/6

The menstrual cup shouldn't be felt when it is placed correctly (just like a tampon or pessary) and you should be able to empty your bladder without difficulty. If you are leaking you may have a fit problem and if overflow a volume problem. 5/6

Knowing the volume of blood a cup is supposed to hold is clearly helpful, especially if you have overflow issues. An I am sure some people prefer the feel of one cup over another (very valid). But if I've missed a clinical trial on cup fitting I would love to see it! 6/6