One of President Donald Trump’s first actions after being sworn in on Jan. 20 was to issue an executive order to begin the process of repealing the Affordable Care Act.

The ACA, also known as Obamacare, has been challenged in federal courts as unconstitutional and denounced by conservative advocacy groups as an example of government largesse and overreach. But the law has also provided more affordable health insurance for an estimated 20 million people who were otherwise uninsured, which has produced the lowest uninsured rate in history, according to the National Center for Health Statistics.

An analysis by personal finance website WalletHub found that an estimated 18 million people would lose healthcare coverage in the first year following the law’s repeal. An estimate from the Committee for a Responsible Federal Budget pegs the cost of repealing the ACA at about $350 billion over the next decade.

If the law is fully repealed, the economic effects could be far-reaching and diverse, depending on what part of the country you live in. Though it wouldn’t go unnoticed anywhere, the ACA’s repeal is expected to have less of an impact in southern states, many of which have not recently expanded Medicaid coverage.

But elsewhere, the effects could be more pronounced. According to the WalletHub report, Massachusetts could see its uninsured population rise by 273 percent in two years, the highest in the nation. New Hampshire could see uncompensated care costs — usually incurred through emergency room visits by uninsured patients — go up by 235 percent.

“The sheer scale of the numbers were surprising,” said Jill Gonzalez, an analyst for WalletHub. “We were surprised to find that, based on recent estimates, by 2026 the rate of uninsured residents will rise to 32 million post-repeal.”

West Virginia, for example, stands to lose about 16,000 jobs and $350 million in tax revenue by 2019, according to a report from the state’s Center on Budget and Policy. Up to 184,000 people in the state would lose health insurance, and the state’s fragile economy could falter with the loss of billions of dollars in federal funds.

“The ACA is much more than a lifeline for hundreds of thousands of West Virginians who have gained health coverage and important patient protections,” said Ted Boettner, executive director of the WVCBP and the author of the report. “It has been a billion-dollar investment in our people that has led to thousands of new jobs during a time when our state’s communities are struggling.”

A replacement plan, Patient Freedom Act of 2017, proposed by four U.S. senators, including Sen. Shelley Moore Capito, R-W.Va., has promised to keep intact the pre-existing conditions and lifetime limits protections; however, the plan specifics did not mention preventive care measures. Capito said in a press release that coverage would be preserved for mental health and substance use disorders.

Proponents of the ACA have also feared loss of coverage for young adults under 26 still on their parents’ plans, but Capito said those individuals would remain protected under the replacement plan. Prescription drug costs for seniors were not addressed in the release about the replacement plan.

Julie Vaughan-Meadors, who lives in Charles Town, West Virginia, near the Maryland border, and her oldest son, Zachary, are hoping those senators make good on their promise to keep protections in place.

Zachary was 23 years old when he was diagnosed with thyroid cancer — a rare diagnosis for a young man. He’s had multiple surgeries along with radioactive iodine ablation treatment, but each summer for the past three years, his cancer has returned.

Zachary, now 26, fears he will not be able to utilize the final months of his health coverage under his parents’ plan if the ACA is repealed.

“He’s scared out of his mind,” Vaughan-Meadors told the Beckley, West Virginia Register Herald. “He thinks he’s going to get dropped tomorrow. We understand as adults it doesn’t happen that quickly, but as a young person, you don’t cope well with cancer to begin with.”

Zachary will graduate from California State University in May with a degree in sociology. He has applied for a job in West Virginia. If he’s hired, he hopes to obtain private insurance through the company. His mom said the biggest concern right now is him having a gap in coverage, or getting denied for having a pre-existing condition.

“Our feeling is the insurance companies will be back in charge, as opposed to having regulation on them,” she said.

The Beckley, West Virginia Register Herald contributed to this story.