• Early onset of menstruation and late onset of menopause.
• Excessive radiation, with an increased risk for women who were given radiation for postpartum mastitis, 
  received prolonged fluoroscopic x-ray evaluations for tuberculosis or were exposed to a large amount of 
  radiation before the age of 40.
• Women with a family history of cancer of the cervix , uterus or colon have a slightly increased risk 
   of developing breast cancer.
• Female descendants of European Jews have a higher than normal risk.
• Obesity with excess caloric and fat intake (three times the usual risk).

At Lower Risk 
• Term pregnancy under age 18. 
• Early menopause.
• Surgical removal of the ovaries before age 37.
• Japanese ancestry (but not if born in America and adopting American dietary habits).

Factors That May Affect Risk, but Whose Role Is Unclear
• Taking female hormones such as postmenopausal estrogens or premenopausal contraceptives.