Yay! I just read High Noon by Nora Roberts and the characters have an oops where they go sans condom. They actually, you know, talk about it after word, clarifying that female is on the pill and male is disease free* but yes to condoms for the future. And really, this is all done in a few sentences, it's not a big deal, but it just makes sense. It doesn't take away from the pretty afterglow, it just makes them sound like responsible adults.
And that's been my point, I know there are authors out there who agree with me (thanks, guys). But, as with the book I read where a character painted her nails and then jumped in the shower, I start to wonder if your characters' lack intelligence. Or are careless. Or stupid. And since, generally, I expect that is not what the author wants me to think about their character, it's is a problem. A really easily fixable one, however.
*I'm not sure why it seems there is typically only a need to determine that the male is disease free, but that seems to be fairly common on Romance-landia.