Well to be perfectly honest I hate the thought of terminating a cats pregnancy like that, but i was faced with that situation when i was spaying the neighbours three cats, I chose not to ask, as i did not want to know, but i don't think any of them were in fact pregnant, i had already rescued ten kittens off them, there was no room anywhere for anymore,but i guess my answer would have to be yes in these type of circumstances,even though it would be very hard for me to have to confront this situation, I would say desperate situations do call for desperate measures sometimes.