Deciding when to get routine mammograms is confusing. Some health groups recommend women begin at age 40 or 45 while another recently opted for age 50. They also differ on whether yearly or every other year is best. The conflicting advice is at least partly because guidelines for breast cancer screening are designed for women at average risk and with no possible cancer symptoms . But breast cancer is so common that it is hard to know who is really “average” and how to balance the pros and cons