In character for me, sex has only come up twice... Once was as a Cha-based Rogue, looking for a place to hide out when the rest of the party had been captured, not wanting to head to inns or anywhere he could easily be found... Not without
other in-character motivations, mind you, but only coming into play because it had a relation to what's happening in-game. (If it doesn't relate to "what's happening", I don't bring it up, beyond the barely-implicit "while Krogdor is getting his armor fixed, I'll be in the tavern trying my charms on the ladies.")
The second time was also brought in for goal-oriented reasons... We were playing a high-level evil campaign, working for Orcus trying to dig up some information on the cult of Demogorgon. We needed to gain this High Priestess' trust, which is something them evil folk don't give out too easily, so I use
charm person as some leverage and seduce her.
Oh, I should mention my character was a mind flayer. She was a tiefling. Not fun to picture (though certainly
funny to picture), but hey, she fell hopelessly in love with me and it got the job done, and I can live with the hit to my Sanity score...
(For note-takers, note that this is in sequence with the writing of The Sexual Confessions of a Mind Flayer, comemmorated in Tonguez' sig, a point of pride for me

Since the sale of the book was what got us into her compound initially, the whole seduction thing just followed naturally... It is hardly my normal modus operandi

)
As far as other players go, I don't think I've ever had any in-game sex beyond the vaguest of implications... This isn't to say it can't be handled maturely or anything, but I think we all just go on the assumption that it's simpler to avoid it than to skirt that line.
At any rate, pregnancy never came up (the first campaign died a few sessions later; in the second campaign, the
tiefling died a few sessions later... but then both I and my DM were operating on the assumption that illithid had no sexual traits particularly congruous with human ones, not to mention that it would be another stretch to imagine the pair being
capable of producing a child, so the question was pretty moot.)
(Edit: Among my many superhero identities, including Superjew and Bums Cigarettes to Minors Man, I am also the Grammar Fairy... So I wanted to point out
Instead of making this a more gender equal idea, its seems to always say that the boys are uh getting the laying while the women are the objects.
Not one bit! Let's look at that phrase, with general gender-specific terms inserted, and a parallel phrase for comparison:
"The man gets laid by the woman."
"A dog gets hit by a car."
Inverting the phrase but preserving the meaning, we get:
"The woman lays the man."
"A car hits a dog."
While "lays" is hardly the intended interpretation of the expression, it still follows from the structure of the expression that it is
the man who is the object of "getting laid," whereas the woman is the subject.
It's rare to find sexual innuendo (or sexual
anything within American/Western culture) that
subjectifies women, so I must stand up in its defense! (Before you accuse me of playing on words, note that the notion of "objectification of women" comes first from the semiotic definition of the object, rather than the way the term is more commonly used.)
Further, I've heard the phrase used as often by women as by men (actually, more... at least in my experience, which I'm sure is biased by many, many factors, the women I've known have been far more willing to talk about sex, and have taken it far less seriously, than the men.)... So I'd say that, as a term itself, it is more or less "equal" along gender lines.
So while I wouldn't say it is (as a term) demeaning of
women, its connotations definitely demean
sex... Which I can see being bothered by, for a number of reasons.