Under new regulations issued Monday, anywhere from 39 percent to 66 percent of employer plans will lose their “grandfathered status” by 2013, according to estimates included with the rules.

For plans that do not fall under the grandfathered status, employers would have to find a plan that complies with the health care bill passed March 23. Whether or not costs for the new plans will be less than grandfathered plans has yet to be seen.

Small businesses would be harder hit than large employers, losing grandfathered status for as few as 49 percent and as many as 80 percent of plans. Employers may keep their plan if it does not raise its prices beyond “reasonable changes” and if it does not cut substantially cut benefits for a particular condition.