Is It Safe To Spay An Elderly Cat ?

I have a female cat who is siamese-burmese cross. She just turned twelve. She may need to be spayed due to several reasons. She started having kittens after she turned 8yrs old. Now she’s sick and tired of it ,but keeps getting pregnant ( I have 5 other cats too ). And the another reason is that she might have some sort of infection. Pyometra, i think. But i hope not. I still need to get her checked by the Vet.
I’m worried that she’s too old , and might not survive the surgery. Since i heard that there is risk with Anesthesia. That some pets just die when given that. i’m afraid of loosing her. please tell me whether it’s safe or not. I don’t know what to do