Pre-existing conditions

As Obamacare reaches a significant milestone, what's it going to be like for the Americans who will be enrolling in health insurance for the first time?

It's hard to find an example of the Supreme Court tossing out a law, where more had already been done to implement it. If even part of health care reform is tossed out, insurers and regulators face a huge task deciding what to undo, and how.

The Supreme Court is about to announces its decision on the health care reform law, which includes guaranteed coverage for people with pre-existing medical conditions. But what exactly counts as one?