• . In this article we are going to walk you through what you need to know if you or anyone you know needs coverage due to a major medical condition. We will also inform you which insurance plans do not cover and which ones cover pre-existing conditions. In health insurance, a pre-existing condition is defined as any medical condition that is chronic or long term such as cancer, pregnancy, sleep apnea to mention some of them. Pre-existing conditions are those that have been diagnosed or treated prior to the enrollment of a new healthcare plan.