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NEW YORK (CNNMoney) — In another merger of health insurance giants, Anthem has agreed to acquire Cigna in a $54 billion deal.

The health services companies said that Anthem, Inc., a Blue Cross and Blue Shield insurer, would buy all of Cigna Corp.’s shares in a cash and stock transaction.

The latest step in a striking consolidation of the insurance industry would leave only three major players.

Earlier this month, Aetna struck a deal to buy Humana for $37 billion.

The third remaining health insurer is UnitedHealth.

Experts say one factor driving the mergers is the Affordable Care Act.

Obamacare has meant more business for major insurers because more Americans have health coverage, but the law has also put more pressure on industry profits.

Some doctors are concerned that the mergers will put too much power in just a handful of insurance companies.

Bigger insurers with more clout could raise premiums and reduce the number of doctors and hospitals in network coverage plans. But health insurers have defended their position.

By Aaron Smith