A unit of Coventry Health Care Inc. has agreed to acquire FirstGuard Health Plan Missouri Inc. from Centene Corp.

Coventry, Bethesda, Md., provides or administers health coverage for 2.5 million U.S. residents, including 373,000 Medicaid beneficiaries.

Centene, St. Louis, manages care for 1.2 million members of Medicaid plans, state children’s health insurance plans and programs for recipients of Supplemental Security Income.

Centene’s FirstGuard Health Plan Missouri unit now serves 32,200 Medicaid beneficiaries, down from 36,000 at the beginning of the year.

Centene bought the Missouri plan along with a bigger Kansas plan in 2004. Centene paid the seller, Swope Community Enterprises, Kansas City, Mo., $93 million for the plans, according to the announcement for the 2004 deal.