My Aya went into heat at 4 months. When from being a happy if crazy kitten to trying to escape the apartment and get herself knocked up pretty quickly. I have heard they are more likely to go into heat early if there are Toms around and we certainly had a large stray population that she came from. At the time I was in Japan and no Vet there does "early spay" that I could find. I took advantage of the fact that we really didn't know exactly how old she was and snuck her in at 5 mos+. They told me she was probably in heat when they did it based on uterine sizeI wonder if local populations differ as breeds would I have only owned moggies (mix breeds) and also sometimes they don't go in to heat all winter! At least the one I have now didn't.
And I am Not saying people shouldn't bother!!! Just that accessible early spay / neuter is not always done.
My two year old goes tomorrow !!!!
She had a 4 day heat last week.