Limited Evidence for Mammograms for Women in Their 40s.
The International Agency for Research on Cancer says that there is limited evidence to support preventative breast cancer screening for women in their 40s. However, they add that for women aged 50 to 75, the research shows that routine mammograms reduce the risk of dying from breast cancer. The revised guidelines recommend routine screening start at age 50 and be done every two years. The expert panel advises that women in their 40s should discuss the pros and cons of mammography screening with their doctor and then make an informed decision.
New England Journal of Medicine, June 2015