If your bladder is full, you’re more likely to get a urine leakage, which increases the possibility of a UTI.
Well, the reason I go to the bathroom after sex is because I have to pee.
You’ve gotta understand something about female anatomy: when you’re having sex there’s the disting possiblity and probability that the urethra is getting rubbed up against. If I have any liquid whatsoever in my bladder and that happens, I generally have to pee.
While I’m in there I also clean up - I personally think semen smells weird when mixed with vaginal fluid and no amount of smoking has made me unable to smell that when I’m trying to go to sleep afterward.
~Tasha
In that case, she’s probably just asking for one quoque. No need to set the bar too high. 
Actually, priapus asked about before, not after. But I think twickster addressed it.
or perhaps it’s just centipede removal
Wow. So that’s the reason for the cigarette afterwards?
If you’re smoking, then reduce speed of copulation and/or use lubrication. No one likes the odor of burnt genetalia.
Which leads to another theory that I’ve heard; that the female orgasm makes cheating more efficient. The claim is that women are more likely to orgasm with a lover than a husband, and therefore are more likely to get pregnant by him.
Hmm, I don’t always go to the bathroom before sex, if caught up in the moment, but I try to. If my bladder is feeling even the slightest bit full, then I want to empty it so I don’t feel like I have to pee at an inopportune moment. I also clean up while I’m in there. Frankly, I wish more men would do the same. I’ve definitely dated guys who smelled pretty funky down there.
I can’t speak to why someone would go to the bathroom right before sex and not clean up.
Help me out here-urine leakage increases chance of a UTI how? Logically-I’d think that flushing the mains would preclude entrance of the nasties causing a UTI. 
Well, the teeth down there usually take care of them…
Do they really need a purpose, people?
Science is all well and good, but some things just don’t have to justify their existence. Next you’ll be asking why puppies are so damned cute.
Shit! This was going to be by next question on GQ. I at least deserve an answer to it, now.
Dunno – paging QtM – just know it’s standard medical advice for preventing UTI’s. Every non-virgin adult woman has had a UTI at some point, often after a period of unusually active sexual activity (aka “honeymoon cystitis”); when you go to the doctor, you get the scrip for antibiotics and a reminder that emptying your bladder before sex is a good idea, because it will decrease the likelihood of future occurences.
Depending on the intelligence of the woman, she may need to hear this more than once before she starts heeding it – but I’m guessing most women over 25 usually do, unless the moment is particularly, ah, urgent.
Does he get a lot of cooter maintenance experience working at the prison? Although I’m sure his treatment history of crotch misadventures has some relevance…
Because they have mammalian-babyish characteristics, and we instinctively find those cute, in order to encourage us to care for our own children.
Which begs the question (to me), why didn’t og place the clitoris closer to the vagana?
Seems like it would be more fun for women. (more orgasms)
But then it seems to do very well where it is!
I’ve thought you were supposed to go to the bathroom after sex to prevent UTIs. The way I heard it, sex increases the chance of a UTI because, in all the rubbing around, bacteria from the vagina can get moved to the urinary tract, where they climb up, multiply, and cause great unpleasantness. Peeing after sex flushes out any little buggers that might’ve migrated.
He’s got plenty of experience outside the slammer – I believe he did family practice for many years.
I thought it was pretty well established that women had orgasms because men had orgasms. The ability to do so is physiological, and established prior to sex differentiation in the womb. Whatever evolutionary advantages it adds are fortunate but incidental.
I think the peeing before is mainly a comfort thing. During sex a certain number of cubic inches of flesh is going to be added to the contents of your pelvic area, pushing other organs aside to make room. Having your bladder empty serves to keep it from being squashed about and possibly having some urine forced out.
As for relating to UTI, what I was told is that having the bladder empty/flaccid reduced how likely it was to be bruised during, well, during. Bruising makes it easier for bacteria to get a foothold, so to speak, whether the bacteria get there as a result of sex or were already floating around in the area.
Yeah, because chicks are totally turned on by the male orgasm. It pretty much just pushes them over the edge. That’s why porn always ends with the money shot. It gives the ladies something to write home about.