LOS ANGELES, (NBC News) In Los Angeles County alone, Medicaid and Children’s Health Insurance cover more babies and toddlers than 40 entire states.

The Trump administration wants to pay its part in block grants. Insurers predict they’d lose billions, and children would lose care.

Advocates say just the threat of cuts is already having an impact.

“There’s a real chilling effect associated with this environment of uncertainty, a chilling effect holding people back from seeing a doctor,” says Mayra Alvarez of The Children’s Partnership.

Experts say young patients now treated in clinics will go to emergency rooms instead.

When California expanded Medicaid under the Affordable Care Act a million more parents and children in the state got coverage. Now they could be among the first to lose it.

Some health care experts believe block grants are a bad way to make medicaid payments to states because it’s a fixed amount of money, predetermined by the federal government, as opposed to paying a fixed amount for each person. It could mean fewer people would be covered for benefits or fewer services would be covered.

An Office of Management and Budget official, speaking on the condition of anonymity, told NBC News that the Trump administration fully supports CHIP reauthorization and expects Congress to pass it quickly.