Portia (a.k.a "Porch Kitty") came to us as an emaciated, sickly stray that showed up at my neighbor's barn, and the vet said that at her age with no evidence of ever having been pregnant before, she was SURELY already spayed. Coupled with the fact that she had no idea how to hunt, we figured she had been an indoor cat that escaped or was dumped out here in the country.
After she got healthy again though... we had a few male cats show up (not unusual, I think there is a "free food and medical care" sign on my place,) and a while later, Portia was looking suspiciously FAT. She's skittish and hard to catch though, so it wasn't until a couple of weeks ago that I got my hands on her and, yep. Kittens are coming.
She picked a nice safe spot behind the stacked hay, under some sheets of metal:
