You can't get a cat desexed until they are 5 months old But they can get pg before that. The feral kitten we hand raised and gave to Mum is nearly due to have her first litter of kittens already.

T, I don't think the issue is if they could or they couldn't have puppies that early, but rather that it's not ideal. She's done terribly well to have that many puppies at a young age. With our dog, we noticed she came on heat at 8 months old so I suppose it's not impossible.