BlueCross and BlueShield of Tennessee said Thursday it is joining other health insurers in voluntarily expediting a popular feature of the health care reform plan adopted last month.

The Tennessee BlueCross plan, the state's biggest health insurer, announced Thursday that it will let thousands of young adults remain on their parents' health insurance policies up to age 26 after June 1 rather than waiting for the Sept. 23 starting date for such coverage under the new federal health care law.

Most BlueCross plans now cover dependents only up to age 24, and many health plans restrict coverage to dependents only up to age 19. But the health care plan signed into law in March will require health insurance eventually to cover any children of parents with health insurance up to age 26, unless the children are eligible for coverage under another plan or are married.

"By making this change in advance of the law, we can ensure that our young members are able to hold on to their coverage and access the care they need," BlueCross President Vicky Gregg said in her announcement of the expanded coverage Thursday.

The extension will apply to fully insured employer accounts for their employees as well as individual policyholders who cover a dependent. But for many BlueCross members whose employers are self-insured, the extended coverage may not be provided until their health plans are renewed following the September implementation of the first phase of the new law, BlueCross spokeswoman Mary Thompson said.

The extension of coverage will apply to all 38 BlueCross plans nationwide and is similar to what United Health Care, Humana and Wellpoint announced earlier this week.

"This is a fairly low cost addition for most insurers -- probably no more than about 1 percent of their costs on an annualized basis -- and it buys a lot of goodwill and political favor," said Jane DuBose, an insurance market analyst for HealthLeaders-InterStudy Research.

Cigna Health Care, Tennessee's second biggest health insurer, has not announced any plans yet to join the early move to the expanded coverage for young adults. Cigna spokesman Chris Curran said "it is still too early to definitely say" how health reform will impact its operations or the projected costs of some of the pending changes.

But U.S. Health and Human Services Secretary Kathleen Sebelius, who asked insurers to make the change in advance of this fall, said she welcomed the companies' voluntary efforts to cover more young adults under their parents' plans.

"Many young adults under the age of 26 have traditionally had a difficult time getting access to -- and affording -- health coverage," she said.