Risk Factors — Reproductive Factors

It has been suggested that the risk of breast cancer can be determined by the amount of exposure of the breast to the hormone estrogen. ref There is an increased risk of breast cancer associated with early menopause, late first full-term pregnancy, and late menopause. There is a reduced risk of breast cancer with early menopause.ref Rather than looking at these elements separately, a more accurate assessment of risk can be made by combining the information of current age, age at first delivery of a child, and time since childbirth. ref

Your age at the birth of your first child is also related to your total exposure to estrogen. When you are pregnant your body is not undergoing dramatic cyclical changes in estrogen. Therefore, women who have more children have lower lifetime exposure to the effects of estrogen.