Unless the litter was very recent, the prominent nipples will be the only visible clue. If she was a stray it is highly probable that she has had at least one litter in the past.
If she has had a litter recently and the pups are still young enough to suckle sometimes, then she will produce milk if you gently but firmly squeeze a nipple starting near to her belly, and sliding to it's end.
If she has had a litter recently and the pups are still young enough to suckle sometimes, then she will produce milk if you gently but firmly squeeze a nipple starting near to her belly, and sliding to it's end.
