The changes to subsidized or free health programs come as private health initiatives that pay for the care of children are running out of money, causing them to limit the number they cover.
Altogether, "thousands of California children are likely to lose health insurance coverage they now have," said E. Richard Brown, the director of UCLA's research center.
These privately run initiatives exist in 30 counties, arranging medical care for children who are not legal residents or whose families earn slightly more than the threshold for public programs.
Enrollment in the initiatives has dropped by 8,000 in the last two years, to 80,000, according to Wendy Lazarus, co-president of the Children's Partnership, a nonprofit advocacy group.
Alameda County's initiative, which insures 1,023 children, is ending next month after one of its funders pulled out.
The Children's Health Initiative of Greater Los Angeles has not added any children older than 5 since October and is scrambling to secure more funding to continue operating through the fall.
Its enrollment dropped 27% in the last three years, to 33,000 children. There are about 200,000 uninsured children in the county.
"We're certainly disappointed that Alameda will close down," said Elaine Batchlor, chief medical officer at L.A. Care, a nonprofit health plan that runs the program.
"We certainly hope we won't have to."
With its large numbers of poor and undocumented children, California has lagged behind most other states in several indicators of health.
For instance, a quarter of the state's children under age 12 had never visited a dentist, according to a report issued last year by the California HealthCare Foundation, an Oakland philanthropy.
The report is based on data from 2005, the most recent year for which information is available.
In 2005, California toddlers were less likely than the national average to receive the recommended doses of five key vaccines, according to a report from the Commonwealth Fund, a nonprofit healthcare foundation in New York.
Karen Davis, the foundation's president, said the rankings suggest that California does not have enough healthcare providers regularly serving its low-income people.
"I know the state has made a concerted effort to cover children, but even in that, it ranks 42nd," she said.
State officials fear that children with insurance may have a harder time finding doctors willing to treat them, because lawmakers cut Medi-Cal reimbursements by 10% this year.
