Companies with big footprints in Obamacare’s expanded markets saw their shares drop Monday, the first trading day after a federal judge ruled the 2010 health care law as unconstitutional.

They face a new era of uncertainty, with hospitals contemplating the loss of billions of dollars over the costs for uninsured patients and insurers trying to figure out what their customer base could look like should the ruling be upheld on appeal.

For now, that’s not a concern. The judge put his decision on hold pending the results of appeals.

Still, the American Hospital Association said it was “extremely disappointed” with the ruling but isn’t panicking just yet.

“I think it’s a blip,” said Melinda Hatton, general counsel for the hospital group. “Wall Street, like everybody else, will recover their senses.”

But investors were skittish Monday. Shares of Centene (-4.8 percent), Molina Healthcare (-8.9 percent) and HCA Healthcare (-2.8 percent), a for-profit hospital operator, fell amid an overall market sell-off in which the Dow Jones Industrial Average dropped 508 points or 2.1 percent.