Maddie-Rudy,
I waited a while thinking Reyna would grow a little more before I had her spayed...she has stayed the exaaaact same weight for like 3 months haha. So my vet said its about time if I wanted to do it...and of course gave me the pro's & cons.
do visit this website...very helpful
http://www.mylittlemia.com/spaying.html
good luck =)