I had Missy spayed when she was 2.5 lbs. She didn't do well with the anaesthetic, they almost lost her.
I'm not sure why she couldn't handle the anaesthetic, she had been put under twice before for leg surgeries. I'm guessing it's because my regular vet did the spay, whereas her other surgeries were done by a specialist. If I were to do it over again, I would be sure to find a vet that had alot of experience working on tinies.
I think it's best to have them spayed, especially if they are tiny. You can't breed them anyways. The health benefits outweigh the risks IMO.
Good Luck with your decision.
