There are four different sets of guidelines on when you should start getting mammograms and how often you need them — and they disagree with each other. A tool called Breast Screening Decisions can help low-risk women figure out what schedule is best.
Mammogram decisions are tricky because more women will get a false-positive result (saying they have cancer when they really don't) than accurate positives. This can lead to more testing and potentially to chemotherapy or surgery that wasn't needed. On the other hand, skipping mammograms means you won't have the ability to detect cancer in its earliest stages.
Many groups, including the US Preventive Services Task Force, say that the best approach is to talk to your doctor about what is right for you. The Breast Screening Decisions tool helps you figure out where to start that discussion. You answer some questions about your risk (How many of your relatives have had breast cancer? At what age did you have your first child?) and it guides you through some things to consider.
For example, it gives visual representations of your false-positive and false-negative rates, like in the screenshot above. It also compares your likelihood of dying of breast cancer versus other diseases under different screening schedules.
At the end of the process, it asks your thoughts on statements like "I'm willing to do anything to detect breast cancer as early as possible" and "I only want to have mammograms if I am at high risk for breast cancer." Then it gives you a printable summary of all of the information that the tool gave you, customised to your risk.
My only gripe is that it doesn't answer the question: the summary doesn't say which, if any, of the existing guidelines are a good fit for you. The printout just displays your answers to the opinion questions rather than trying to tell you what your opinions mean. But that's sort of the point: to get the real answer, you'll have to talk to your doctor.