More than 3.1 million Americans ages 19 through 25 are now covered by their parents’ medical insurance policies due to the health reform law, the Department of Health and Human Services announced Tuesday.

That’s up from 2.5 million in December, reports show. The number of insured for that age group has increased to 75 percent.

"This policy doesn't just give young adults and their families peace of mind, it also gives them freedom,” said HHS Secretary Kathleen Sebelius. “It means that as they begin their careers, they will be free to make choices based on what they want to do, not on where they can get health insurance.”

The law mandates that insurers allow young adults to remain on their parents’ plans until they turn 26, even if they move away from home or graduate from school.

Though the PPACA in its entirety isn’t favorable—with an approval rate of 37 percent, according to the Kaiser Family Foundation—the young adult coverage provision has been one of the most popular provisions with 71 percent of the public viewing it favorably.

Even insurance giants UnitedHealth, Humana and Aetna have said they intend to keep the provision regardless of what the Supreme Court decides about the law.

Before the PPACA, young adults were the age group least likely to have health insurance. Not only were young adults more likely to be uninsured, they were also more than twice as likely as older adults to lose private insurance coverage once they had it. Some young adults lost coverage when they became too old to qualify as a dependent on their parents' plans, and others lost coverage as they graduated from school or changed jobs.

The Commonwealth Fund released a similar report earlier in the month, which showed 13.7 million young adults stayed on or joined their parents’ health plans, including 6.6 million who wouldn't have been able to do so without the PPACA.

Commonwealth says the HHS report is consistent with what they found, but that Commonwealth's number was larger "because it included young adults who were previously uninsured—so that would include the 3.1 million that HHS reported—and also included young adults who had been insured under some different kind of coverage, like individual coverage, and they switched on to their parents' coverage," explains Commonwealth Fund spokesperson Mary Mahon.

A ruling by the Supreme Court on the fate of the PPACA is expected next week.