Some risk factors for breast cancer&mdash;such as age&mdash;can't be avoided.
On the other hand, there are some risks that you can control. It's important to be aware both of the risks you can't change and of those you can do something about. 
Risks you can't control 
Family history. If people in your family have had breast cancer, you may have a higher risk for the disease. According to the <a href="[BASEDOMAIN]/healthinfo/BounceLink.aspx?Shortcut=cancersoc" target="_blank">American Cancer Society</a> (ACS), this is especially true if you have multiple close relatives who had breast cancer. Overall, less than 15 percent of women with breast cancer have a family member with the disease.
Genes. Some gene mutations can increase your risk for breast cancer. If you inherit an altered BRCA1 or BRCA2 gene, your risk of breast cancer increases dramatically. Other genes are under study for their role in the development of breast cancer.
Testing is available for some of these genes, but the ACS strongly recommends talking to a genetic counselor, nurse or doctor with expertise in these tests before you have them done. The benefits and risks are different for every woman.
Age. Your risk of breast cancer increases sharply around age 55. That's part of the reason the ACS recommends regular mammograms for all women age 45 and older. 
Previous cancer. Having cancer in one breast increases your risk for cancer in the other breast or for a second cancer in the same breast.
Early menarche. If your first menstrual period occurred before you were 12, your risk of breast cancer is slightly higher than women whose first period occurred later. 
Late menopause. Studies show that women who reach menopause after age 55 have an increased risk for breast cancer. 
Radiation therapy to the chest. Women who have had radiation therapy to the chest as children or young adults are at higher risk for breast cancer, especially if the therapy was given while the breasts were still developing in adolescence.
Diethylstilbestrol (DES). If your mother took DES while she was pregnant with you, you have a higher risk of breast cancer. From 1938 until 1971, this drug was prescribed for some women to help prevent miscarriage.
Some noncancerous breast changes. Some types of breast conditions are linked to a higher risk for breast cancer. Some conditions raise the risk only slightly, while others can raise it by as much as five times. If you've had a breast biopsy, your doctor can help you understand how the results reflect on your breast cancer risk.
Risks you can control 
Hormones. Using hormone therapy after menopause, especially if it includes estrogen and progesterone, increases breast cancer risk. Women who use oral contraceptives have a slightly higher breast cancer risk than women who have never used them.
Obesity. Being overweight can increase breast cancer risk, especially after menopause. The increased risk seems to only apply to women who became overweight as adults. 
Alcohol. Research clearly shows that drinking alcohol increases breast cancer risk, according to the ACS. Women who have one drink a day have a slightly increased risk, and women who drink more than that have about a 20 percent higher risk than women who don't drink alcohol. 
Exercise. Women who get regular exercise have a lower risk for breast cancer. The ACS recommends 150 minutes of moderate-intensity activity or 75 minutes of vigorous activity each week. 
Pregnancies. Women with no biological children have a higher risk for breast cancer, as do women who gave birth for the first time at age 30 or older. 
Breastfeeding. Women who breastfeed their children, especially if they breastfeed for 1.5 to 2 years, may have a lower risk of breast cancer. 
Assessing your risk
If you're concerned about your risk for breast cancer, talk to your doctor. He or she may recommend earlier or more frequent screenings than normal, medicines, or other approaches to reducing your risk.
reviewed 12/11/2018

Understanding breast cancer risks

No matter what your risks, you can help protect yourself from breast cancer.