Certain pieces of a woman's health history can mean that her risk of developing breast cancer is higher. For most women, these are not factors that can be changed, but many women want to know about risks that may exist.
The risk of developing breast cancer increases as you get older- that is just because more women get breast cancer in their 60s and 70s than in their 30s or 40s. Women who have their first menstrual period before age 12 have a slightly higher risk of breast cancer. This is thought to be because they will have a longer lifetime exposure to estrogen in their bodies. The age of a woman at her first live birth of a child can affect risk, but the effect varies, depending on the number of first-degree relatives who have been diagnosed with breast cancer. For women with 2 or more 1st degree relatives with a diagnosis of breast cancer, risk decreases with an older age at first live birth. For women with no family history, risk increases with older age at first live birth.
Having one or more first-degree relatives with a diagnosis of breast cancer increases risk. There is an increase in risk for women who have had a breast biopsy in the past, particularly if the biopsy found atypical hyperplasia. This is due to whatever breast changes resulted in the biopsy and not the biopsy itself.
Researchers have created a program, called the Breast Cancer Risk Assessment Tool, that takes all these factors into consideration and calculates an estimated risk of developing breast cancer in the next 5 years and in the woman's lifetime. These calculations are based on the Gail Model, a statistical model for determining risk. Learn more about the Model or use the tool.