Organizations representing hospitals and specialties reacted negatively to an estimate the Affordable Care Act (ACA) replacement passed by House Republicans would result in 23 million fewer people having insurance by 2026.

The Congressional Budget Office (CBO) report on the American Health Care Act (AHCA) projected a slightly smaller rise in the number of uninsured than a previous version of the bill. It also said premiums would be lower on average after 2020, but mostly thanks to rolling back ACA insurance regulations, allowing states to waive currently required benefits so insurers could offer skimpier plans.

“As we have said, any health reforms must be guided by ensuring that millions of people across the country don't lose access to their healthcare coverage,” said American Hospital Association President and CEO Rick Pollack. “We cannot support legislation that the CBO clearly indicates would jeopardize that coverage for millions of Americans.”

Similar statements of opposition came from the American Medical Association and Kaiser Permanente Chairman and CEO Bernard Tyson.

Some specialty groups dug into exactly how the CBO projected their patients could be impacted. For example, one of the insurance benefits states could waive is maternity care. The CBO said customers in waiver states who have to purchase maternity benefits separately may have to pay more than $1,000 per month, close to the full cost of care, because insurers would expect most purchasers to use those benefits.

That was one of several reasons the American Congress of Obstetricians and Gynecologists (ACOG) has come out against the AHCA.

“Our bottom line remains the same: Congress must not turn back the clock on women’s health,” said ACOG President Haywood Brown, MD, in a statement to HealthExec.

Other groups focused on the broader impact of the CBO estimate, such as how the individual market in areas with one-sixth of the U.S. population could become unstable or how state waivers could allow insurers to charge people with pre-existing conditions more for coverage and likely price them out of the market.

“These practices would also threaten the financial stability of millions of individuals and families, if, for example, protections against annual and lifetime spending caps are waived,” said American Academy of Family Physicians (AAFP) President John Meigs Jr., MD.

On the political side, the reaction from Democrats largely mirrored that of the medical organizations, while Republicans who supported the AHCA focused on the estimated $119 billion reduction to the federal deficit and the promise of lower premiums.

Some Senate Republicans, however, were concerned with the CBO score on the AHCA. Sen. Susan Collins, R-Maine, pointed to the estimate that a 64-year-old making $26,500 per year would see their premiums on the individual market soar from $1,700 to as high as $16,100—an 850 percent increase. Instead of the AHCA, she encouraged members of both parties to support the Patient Freedom Act introduced by her and Louisiana Sen. Bill Cassidy, MD, earlier this year.

Opposition to the AHCA among Senate Republicans is notable, as the party can afford to lose only two votes among their caucus and still pass the legislation.