Melissa, don't stress yourself out about this. It is the healthiest best choice you can make for Presley and I'm sure the vet has done hundreds of these surgeries without incident. Given your circumstance I'm sure that's the only reason that Presley will have to stay over, not because there is a big risk. Presley will thank you later. Trust me, having had to deal with Jessie being in heat and subsequent pregnancy (which was terminated when we had her spayed at the recommendation of the vet), it's NOT a fun thing...she was worse than ANY woman I've EVER seen PMSing! lol

Good luck and let us know how it goes. We'll be thinking of Presley!!