Prior to the passage of the Affordable Care Act (ACA), insurance companies could charge people with pre-existing conditions whatever they wanted or deny them coverage altogether. One of the most popular features of the ACA is the ban on pre-existing condition exclusions. In addition, plans are no longer allowed to base your premiums on your medical history. This levels the playing field between those who are fortunate to be in good health and those who have not been as lucky.
There is an exception to this feature, however. Short-term health plans (those providing coverage for less than 12 months) and grandfathered health plans (those in effect since March 2010 that have not been substantially changed) can still exclude pre-existing conditions or charge more for them.