This one goes without saying, right? You get breast implants, you're probably not Googling, "Why are my boobs bigger?" What you may not. And we have discovered your boobs stop growing and changing much done with, you may notice that things don't necessarily go back to normal. My agonising period pains are down to having TWO vaginas and wombs. Primary breast growth occurs during puberty, and breasts stop growing typically about years after a girl's first period. This is usually around age After this. Guys wonder when their voices will get deeper, when they'll need to shave, or when their penises will grow. But it's perfectly normal for breast development to start anytime between the ages of 7 and A girl's first menstrual period usually happens about 2 to 2½ years after breast development begins. Is This My Body?