Maya went into heat at 14 months. I had her spayed shortly after. She had leg surgery at the time I would have normally spayed her and then since she was so skinny and recovering from that, I just didn't get her spayed. So, I don't know why, but I was shocked when she went into heat. Of course, it was right after my leg surgery that had me in a full body brace. Ugh. Peach got spayed last week so Maya was my only dog that I could tell you when they went into season.