KANSAS CITY, Mo. (AP) — Health insurer Centene Corp. said Friday that the nearly 40 Missouri counties where it will launch coverage on Affordable Care Act insurance exchanges next year include roughly two dozen that would otherwise have been without an insurer.

Missouri-based Centene Corp.'s announcement Friday came 17 days after it said it would foray into the Missouri exchanges even as others are either withdrawing from such markets or proposing steep price hikes to remain. Consumer rights advocates celebrated the announcement, saying something is better than nothing.

Centene's planned offer...