The $5.6 billion Aetna-Coventry Health Care merger is the biggest in the health care sector since President Barack Obama enacted the reform law in March 2010. The deal will give Aetna, the third-largest health insurer in the U.S., a big increase in Medicare and Medicaid customers, including poor elderly people on both programs, and in the number of people who buy insurance on their own or get coverage from small businesses. Aetna will gain 5 million new customers when the merger is complete and stands to get even more in the near future.

Health insurance companies, hospitals and other players are merging into bigger entities in hopes of restraining their own costs and grabbing larger shares of the markets as they are reshaped by health care reform. The health insurance industry is undergoing a transformation as a result of the health care reform law. Twenty-five million people will buy health insurance on the law's regulated "exchange" marketplaces in the states, according to the Congressional Budget Office. Many of those small businesses and people who don't receive health benefits from their jobs will get federal tax credits. Medicaid will also add 11 million poor people and states are expected to contract with private health insurance companies to cover them.

In addition to boosting its Medicare and Medicaid business, the merger also gives Aetna better access to the "lower end" of the health insurance market -- people who will switch between Medicaid, individual insurance, and small business plans. The health insurance law will expand that pool of customers through the exchanges and subsidies. The health insurance industry lobbied against the law in 2009 and 2010 and Aetna, at least, has continued to campaign against it. In 2011, Aetna, based out of Hartford, Conn., gave $3.3 million to the American Action Network, a conservative non-profit organization,