Oral Contraceptives

• The National Cancer Institute (NCI) states that certain oral contraceptives may increase the risk of breast cancer.
  
  

Hormone Replacement Therapy

• According to the NCI, the use of hormone replacement therapy increases the risk of breast cancer. The NCI states that a recent study done by Swedish researchers has determined that breast cancer survivors who took hormone replacement therapy (HRT) had three times the risk of breast cancer recurrence than those who didn't take HRT.
  
  

Alcohol

• Drinking one alcoholic drink a day slightly increases a woman's risk for breast cancer. Consuming two or more drinks daily increases a woman's risk 1.5 times more than the risk that exists for women who do not consume alcohol.
  
  

Breast Radiation

• The American Cancer Society says that the risk of breast cancer increases for women who have had breast radiation prior to age 40. The risk level is higher if the radiation occurred during teen years.
  
  

Diethylstilbestrol (DES)

• Women who were given diethylstilbestrol (DES) and women whose mothers were given DES during pregnancy have an increased risk of breast cancer. Diethylstilbestrol is a drug that was given to pregnant women from the 1950s to early 1970s to prevent miscarriages.