Sudden Breast Growth In 20s. This occurs due to growth of the milk producing tissues and milk ducts as your body prepares for breastfeeding your breasts gradually return to their pre pregnancy size after you stop breastfeeding or shortly after delivery if you opt for formula feeding. Your 20s and 30s are obviously prime baby making time so changes brought on by pregnancy are worth noting.
This is due to differences in your reproductive hormone levels caused by the natural process of aging. Once you start ovulating and having a menstrual cycle the milk ducts will form glands. These changes are harmless and may make the breasts feel lumpy and sometimes cause pain.
Both breasts differ in size and shape but this is usually so minor that most women will not notice it.
Pregnancy causes breast enlargement often an increase of several bra cup sizes. Birth puberty and menopause stage. As you age the tissue and structure of your breasts begin to change. Fibrocystic changes are another cause of breast growth in women in their 20s.