As I said, vet care is not my responsibility. The responsibilities of a foster carer are not the same as those of an owner. I can't take the fosters for surgery or other treatment without permission even if I want to pay for it, nor can I sell or give them away, nor send them to another carer without permission, nor euthanase them for any reason even if it's the best thing for the animal. They do not belong to me.
My own cats go to the vet as and when I think they need to. I do that for them even if it means the human family have to eat toast and beans for a week.
When she came into care the rescue was told that she was thought to be pregnant. We proceeded on that basis. It could have been a vet who examined her before she was sent here, I don't know; I'm not privy to the internal workings of the pound. She got a bigger tummy as expected, and developed very respectable breasts and pregnancy-appropriate behaviours. It was all quite consistent until right at the end, when instead of having what we thought would be one kitten, she went into heat. It's uncommon in cats but it does happen.
Surely it's a much better scenario than the more usual one of a pregnancy in a pound cat not being recognised and kittens unexpectedly appearing in an unprepared foster home.
There's a narrow window in which a pregnancy can be palpated, between the foetuses getting big enough to feel and the various structures and fluids inside the cat obscuring them. After that point you're limited to ultrasound and, later in the pregnancy, xrays. Vets are notoriously bad at estimating due dates and kitten numbers by palpation. I don't know any rescue groups who have money to splash around getting scans or xrays done in the absence of an actual problem.
I will indeed link the new thread when I start it 