(CNN) House GOP leaders have agreed to change an Obamacare provision that guarantees all health insurers cover services such as maternity, mental health and prescription drugs.
The dramatic shift would strike a blow at the heart of Obamacare, even while the GOP legislation says it protects coverage for pre-existing conditions.
The change came as an appeal to conservatives, after House Freedom Caucus members lobbied President Donald Trump this week to eliminate the provision, which was not mentioned in the GOP health care plan that House leaders originally floated.
Instead, Congress would leave it up to states to decide which benefits policies must contain.
The Affordable Care Act -- also known as Obamacare -- requires insurers to cover 10 "essential health benefits" in all plans sold on the individual and small group markets. It has made coverage more comprehensive and prevented insurers from selling skimpy plans that were cheap, but didn't offer many benefits -- often leaving consumers with big bills if they needed care.
Prior to the Affordable Care Act, costly items such maternity, prescription drugs, mental health and substance abuse were often not an option for many buying policies in the individual market.
Removing the provision could greatly weaken the law's protection of those with pre-existing conditions. Without the requirement to cover comprehensive policies, insurers could opt exclude some of the priciest services that sick Americans need. Carriers would also no longer have to cover annual exams and preventative tests free of charge.
On the flip side, the measure has also driven up premiums and restricted consumers' choice to buy more limited coverage. Enrollees who don't have kids question why they have to pay for pediatric services, while those not of childbearing age argue they shouldn't have to pay for maternity benefits. Others want to be able to once again buy "catastrophic plans" that come with high deductibles but cover policyholders in case of serious accidents or illnesses.
Republicans have long wanted to get rid of the essential health benefits provision, which is key to their pledge to reduce premiums and offer choice to consumers.
House leadership did not originally include it because doing so would likely run afoul of Senate rules governing budget reconciliation, the procedure being used to avoid a Democratic filibuster that Republicans won't be able to break.
Jettisoning the provision was in the draft plan that was leaked last month, but did not make it into the final bill.
What's inside the Republican health care bill?
Even before Thursday's dramatic shift, congressional Republicans and administration officials were chipping away at the mandate. The GOP bill calls for relieving states of covering the benefits in their Medicaid plans, sparking an outcry that the move would hurt efforts to treat the opioid epidemic.
Also, Health and Human Services Secretary Tom Price told House Republicans last week that he plans to weaken the provision by changing the regulations governing it. While the 10 benefits are spelled out in the law, the health secretary wields a lot of power over how the provision is actually implemented.
Maternity coverage could be high on the list to be watered down. Seema Verma, who runs the Centers for Medicaid & Medicare Services, said during her congressional hearing that she doesn't think the benefit should be required in every policy.