Hello all. Brooklyn is scheduled to be spayed on Monday 10/11. She's 5.5 months old and about 6lbs already

. So far she's very healthy, up to date on all her vaccinations, flea preventative, and heart worm preventative. Here's my question. I've read where people wait until the baby teeth fall out to get their puppy spayed. Is that so that if the vet has to pull some he can do it while the pup is already under anesthesia or is there some other reason?
She isn't my first dog or first spay but she is my first yorkie and I just wanted to know if there's any additional special things I should know.
Thanks in advance.