Excessive dark circles on the breasts may be a normal physiological reaction to pregnancy or breastfeeding, or it may be caused by genetic factors or high hormone levels in the body. 1. Physiological reaction: Women will have dark circles on their breasts during pregnancy or breastfeeding, which is due to higher hormone levels in women’s bodies. Breast dark circles during pregnancy or breastfeeding will not cause any adverse effect on women, so women do not need to worry too much. 2. Genetic factors: some women have large dark circles on their breasts, which are caused by congenital genetic factors. If one or both parents have a large range of dark circles on their breasts, their children’s dark circles on their breasts are likely to be larger and deeper than the average. 3. High level of hormone in the body: large dark circles in female breasts may be caused by high hormone level in the body due to various diseases, such as tumors in the pituitary gland will lead to higher level of sex hormone in the body of women, which will lead to the appearance of large dark circles in the breasts. Women should pay attention to observe their own conditions, if the breasts are too large, need to consult a doctor in time to clarify the cause.