Quick summary
Knowing the risk factors that contribute to breast cancer can help you evaluate the likelihood of getting the disease. In some cases, it's possible to make changes now that will improve your chances of avoiding it. Here's what researchers know about breast cancer risks.
Menstruating longer, having children late
Breast cancer risk is affected by changes in hormone levels throughout life. Longer periods of high estrogen levels lead to a higher risk of breast cancer -- for example, women who had their first period before the age of 12, entered menopause later than 55, and either didn't have children or had their first child when they were older than 30. In contrast, becoming pregnant at an early age or having multiple children decreases a woman's risk of breast cancer.
Similarly, breastfeeding for one and a half or two years affects a woman's hormone levels and thus decreases her breast cancer risk.
