Recently having a conversation with my mother-in-law and four sisters-in-laws, the subject of Kegel exercise was brought up.
I stated that one of the recommended ways to start strengthening your pelvic floor is to halt your urination for a few seconds and then continue. The five of them told me that it leads to increased in UTIs. They all claimed to have been told this by their respective gynaecologists.
However, after researching this myself, the only thing I found was this article which states that you should try it, but:
However, you should use this method for learning purposes only. It is not a good idea to start and stop your urine regularly, or to frequently do Kegel exercises when you have a full bladder. Incomplete emptying of the bladder can raise your risk for a urinary tract infection (UTI).
Web MD, and other medical sites, all state that holding a full bladder for a long time may cause a UTI, but since you're just stopping the flow for a few seconds, and then continuing to empty your bladder, I don't see the issue.