Major health insurance companies in California and other states have decided to stop selling policies for children rather than comply with a new federal healthcare law that bars them from rejecting youngsters with preexisting medical conditions.

Anthem Blue Cross, Aetna Inc. and others will halt new child-only policies in California, Illinois, Florida, Connecticut and elsewhere as early as Thursday when provisions of the nation’s new healthcare law take effect, including a requirement that insurers cover children under age 19 regardless of their health histories.

The action will apply only to new coverage sought for children and not to existing child-only plans, family policies or insurance provided to youngsters through their parents’ employers. An estimated 80,000 California children currently without insurance - and as many as 500,000 nationwide - would be affected, according to experts.

Insurers said they were acting because the new federal requirement could create huge and unexpected costs for covering children. They said the rule might prompt parents to buy policies only after their kids became sick, producing a glut of ill youngsters to insure. As a result, they said, many companies would flee the marketplace, leaving behind a handful to shoulder a huge financial burden.

The insurers said they now sell […]