Risk factors aren’t exclusively related to family history. In fact, environmental factors contribute 80% to a woman’s risk of developing breast cancer — only 20% is due to family history. Many variables can increase the risk of breast cancer, including: ‍ Age The risk for breast cancer increases with age; most breast cancers are diagnosed after age 50. ‍Genetic mutations Women with inherited changes (mutations) to certain genes, such as BRCA1 and BRCA2, have a higher risk of breast and ovarian cancer. (According to the CDC, about 1 in every 500 women in the US has a mutation in either her BRCA1 or BRCA2 gene.) ‍Early menstrual period Women who start their periods before age 12 are exposed to hormones longer, slightly increasing their risk of breast cancer. ‍Late or no pregnancy Women who are pregnant for the first time after age 30 and those who never have a full-term pregnancy are at increased risk of breast cancer.  ‍Starting menopause after age 55 Women who start menopause after age 55 are exposed to hormones longer, slightly increasing their risk of breast cancer. ‍Not being physically active Women who are not physically active have a higher risk of getting breast cancer. ‍Being overweight or obese after menopause Older women who are overweight or obese have a higher risk of getting breast cancer than those at a normal weight. ‍Having dense breasts Dense breasts have more connective tissue than fatty tissue, which can sometimes make it hard to see tumors on a mammogram. Women with dense breasts are more likely to get breast cancer. ‍Using combination hormone therapy Taking hormones to replace missing estrogen and progesterone in menopause for more than five years raises the risk for breast cancer.  ‍Taking oral contraceptives (birth control pills) Certain forms of oral contraceptive pills have been found to raise breast cancer risk. ‍Personal history of breast cancer Women who have had breast cancer are more likely to get breast cancer a second time. ‍Personal history of certain non-cancerous breast diseases Some non-cancerous breast diseases, such as atypical hyperplasia or lobular carcinoma, are associated with a higher risk of breast cancer. ‍Family history of breast cancer A woman’s risk for breast cancer is higher if she has a mother, sister, daughter (i.e. first-degree relative), or multiple family members on either her mother’s or father’s side of the family who have had breast cancer. Having a first-degree male relative with breast cancer also raises a woman’s risk. ‍Previous treatment using radiation therapy Women who have had radiation therapy to the chest or breasts (e.g. treatment of Hodgkin’s lymphoma) before age 30 have a higher risk of breast cancer later in life. ‍Women who took the drug diethylstilbestrol (DES) This was given to some pregnant women in the United States between 1940 and 1971 to prevent miscarriage, have a higher risk of breast cancer. Women whose mothers took DES while pregnant with them are also at risk. ‍Drinking alcohol Studies show that a woman’s risk for breast cancer increases with the more alcohol she drinks.