Does urinating kill sperm leftover in the urethra?
I want to know if sperms leftover in the urethra will be killed by urinating. If so, does that mean precum will not contain sperms after urination?
Pre-cum can contain sperm (especially by picking up sperm left behind in the urethra from a previous ejaculation), but if you urinate between sexual encounters, nearly all the remaining sperm in the urethra will be flushed out.
Interestingly enough, even though I couldn’t find any literature on whether urine kills sperm, one could assume that it does, extrapolating from the theory that pre-cum is alkaline to neutralize the acidic remnants of urine present in the urethra (in order to create a “safe passage” for your sperm). Hence, the converse must also be true – ie the acidity of your pee damages/kills sperm.
So if you’ve urinated several times between ejaculations, the likelihood is that your pre-cum will contain so little sperm that it wouldn’t present any pregnancy risk (which is what I presume you are asking about).
Having said that, about 73% of couples who use the “withdrawal method” become pregnant within 1 year. Something to bear in mind, if you want to avoid a pregnancy!
A study done 20 years ago in-vitro showed that sperm motility(health) was reduced by urine ammonia. Beyond that, there is no clear evidence on whether urine is spermicidal, excepting the clearing through physical means of residual semen post-ejaculation.
I would assume as Dr Ethan has that this is pertaining to whether it is safe for further sexual encounters post urination as part of contraception. Barrier methods like condoms would still be advised to avoid unwanted pregnancies.
Do keep safe and protected!