As far as I know, it's a myth. How can you stop growing when you get your period when some girls get periods at age 10? Don't worry, maybe you're just a late bloomer :) if you want to be sure, try talking to parents or your family doctor. If your mom's chest is small, however, it might tell you a few things about your own...That's as far as I know. Wish I could help you more.

You don't stop growing when your period starts, that's just crazy. I started my period when I was nine years old and when I was nine I had no boobs, so that just tell you that you don't stop growing when you start your period. Girls stop growing before they reach 21 so you have plenty of time to develope.