NON-MODIFIABLE RISK FACTORS   MODIFIABLE RISK FACTORS    Gender   Age   Personal breast cancer history   Family history   Proliferative breast conditions   Breast density   Early menstruation/ Late menopause    Radiation exposure > Reproduction   Breastfeeding   Hormone replacement therapy   Oral contraceptives   Body weight   Physical activity   Alcohol use   Tobacco smoke (for younger women)

REPRODUCTION

There is evidence that carrying a pregnancy to term affects a woman's risk for breast cancer.

First, the risk of developing breast cancer is higher during pregnancy. The effect may last for up to several years following the birth of the child. It is likely a result of the hormonal changes during reproduction that promote cell growth in breast tissue. Despite the increased risk during pregnancy, the overall risk level during a woman's childbearing years is low compared to the risk later in life.

Second, women who never carry a full-term pregnancy are at increased risk of breast cancer. The hormones of a pregnancy carried to term mature the breast tissue in a way that seems to protect against breast cancer.

Third, women who have their first full-term pregnancy after the age of 30 – 35 have a slightly higher risk of breast cancer than women who have at least one full-term pregnancy at an earlier age. This is thought to be because the younger a woman is when she first gives birth, the less time her breast cells spend in the partially developed state which is more susceptible to breast cancer.