This is a big week for the future of American health insurance.  

A mammoth offer from Aetna to buy Humana for $37 billion is set to be approved by shareholders this week, three months after the tentative deal was announced by company executives.  

Shareholders will also vote on Centene's $6.3 billion offer for Health Net. Both companies specialize in health plans through government-subsidized programs, including Medicare, Medicaid and the Obamacare state insurance exchanges.  

CNBC reports that independent proxy advisers, Institutional Shareholders Service and Glass Lewis, recommended both deals based on potential cost savings, and the belief that the newly-formed companies would be more efficient.  

But while the Centene deal has already gotten the nod from the federal Justice Departmentbut the Aetna-Humana deal could require a significant amount of additional scrutiny from federal regulators before it is approved. 

In evaluating the Aetna-Humana deal, regulators will try to determine whether the merger, along with that of Cigna and Anthem, will negatively affect health care consumers. The concern is that too much consolidation of payers could limit options –– particularly in certain parts of the country –– and leave patients and providers at the mercy of an insurance monopoly.  

A number of experts and industry groups have weighed in on the potential pros and cons to the mergers. While bolstering the strength of one insurer can force competitors to provide consumers better options, too much consolidation can leave consumers with no competition at all.