The proposed $37 billion merger between health insurers Aetna Inc. and Humana Inc. will face regulatory scrutiny Wednesday in a hearing by the California Department of Insurance.

The 9 a.m. hearing in Room 113 of the State Capitol in Sacramento comes on the heels of last month’s meeting over Anthem Inc.’s plan to acquire Cigna Corp. for $54.2 billion, which would create the country’s largest health insurer. Anthem sells policies under the Blue Cross name in California.

“In combination, these megamergers are a real worry,” said Betsy Imholz, special projects director at Consumers Union, the policy and advocacy division of Consumer Reports. “Although they claim efficiencies and synergies, we’ve never seen those benefits or any saving passed along to consumers.”

The state’s two insurance regulators, the Department of Insurance and the Department of Managed Health Care, have both held hearings on the Anthem merger but have not made a decision. Wednesday’s insurance department hearing on Aetna’s proposed acquisition follows a hearing held by the Department of Managed Health Care.

California and federal regulators have approved a merger on a smaller scale — the $6.8 billion acquisition of Woodland Hills insurer Health Net by Centene Corp., which is from St. Louis. The agencies placed several conditions on the approval, including requiring Centene to invest in California’s health safety-net infrastructure for low-income residents.

Antitrust officials at the U.S. Justice Department are also reviewing the other two deals.

In California, the Anthem-Cigna merger is a much bigger deal due to its size and the fact that Anthem is offered through the state’s insurance exchange, Covered California, which was created by the Affordable Care Act. Aetna does not participate in the exchange.

Carmen Balber, executive director of Consumer Watchdog, said the advocacy group is concentrating on the Anthem-Cigna deal because Aetna and Humana are not large players in California.

But Balber said she is concerned about the merger on a national level. “We have five major (U.S.) insurance companies,” Balber said. “If this merger, along with the Anthem merger, goes through, we’ll have three.”

Victoria Colliver is a San Francisco Chronicle staff writer. Email: [email protected] Twitter: @vcolliver