Breast development is a normal part of puberty, which starts at the onset of a girl’s reproductive system, between the ages of 8 and 13. The breasts start to form mammary glands and fatty tissue during this time. The size of the breasts is ultimately determined by a girl’s genetics and weight. Breasts grow most rapidly between the ages of 13 and 17.
The age at which breast growth stops is highly variable, depending on individual genes and other factors. Many girls’ boobs stop growing during the late teens and early 20s, though some may continue to grow until their 30s or 40s.
Girls often feel a tingling sensation in the area of their nipples as their boobs are developing. They may also need to go shopping for bras in a larger size. It’s common for one breast to grow more than the other, which is called asymmetry. In adulthood, this can sometimes lead to breast sagging.
Even after a girl’s boobs reach full size, they can continue to change as hormone levels fluctuate throughout the course of their life. They may be larger during pregnancy and after breastfeeding, then smaller again when the breasts have stopped producing milk. They can also shrink due to the natural aging process and decrease in estrogen, especially during perimenopause or menopause. However, these changes are normal and aren’t a sign of health issues.