The Associated PressAetna Inc. follows a tough lead on Thursday when it becomes the second major health insurer to report third-quarter results. WHAT TO WATCH FOR: Aetna competitor UnitedHealth Group Inc., the largest U.S. health insurer, said last week its third-quarter earnings jumped 23 percent, and it raised its 2012 earnings forecast for the third time this year. UnitedHealth said its results were helped, in part, by a $390 million benefit it recorded because claims left over from earlier periods came in lower than expected, which freed up money held in reserve. Analysts will be looking to see whether Hartford, Conn.-based Aetna records a similar benefit. They also will want to hear what Aetna leaders have to say about 2013. Insurers usually start giving analysts a sense for what to expect in the new year when they report third-quarter numbers. UnitedHealth, for instance, told analysts it expects growth next year, but high unemployment rates and tight government budgets could squeeze its private insurance and Medicare and Medicaid businesses. Investors also may hear more about the major acquisition Aetna announced in August. The insurer plans to spend $5.7 billion to buy Coventry Health Care Inc., a Medicare and Medicaid coverage provider. The deal will broaden Aetna's Medicaid business a few months before millions of people are expected to become eligible for the state- and federally funded program for the needy and disabled under President Barack Obama's massive health care overhaul. It also will boost the company's portion of business from the federally funded Medicare program, which covers seniors over age 65 and those who are disabled, at a time when interest in these plans is growing in part because baby boomers are aging. WHY IT MATTERS: Aetna is the third-largest health insurer, trailing only UnitedHealth and WellPoint Inc. in enrollment. Aetna provides health insurance for about 18 million people. It also sells dental, group life and disability coverage.