WellPoint Inc., the largest U.S. health insurer based on membership, reports first-quarter results Wednesday before the market opens.

WHAT TO WATCH FOR: Many health insurance investors breathed a sigh of relief April 21 when UnitedHealth Group Inc. reported a 13 percent jump in first-quarter net income and a performance that trumped Wall Street expectations.

Insurers entered 2011 facing a new health care overhaul rule that essentially requires them to pay out a minimum percentage of premiums on medical claims, or issue rebates to consumers. Investors were concerned that the requirement for that measure, known as a medical-loss ratio, would affect profits.

But analysts said UnitedHealth's performance showed that health insurers can still do well despite the requirement, and the company's performance bodes well for the rest of the managed care sector.

UnitedHealth also said it continued to benefit from slower growth in health care use, a trend that helped several health insurers, including WellPoint, in the final quarters of 2010.

WellPoint has said it expects use to return to normal levels this year.

The Indianapolis-based company has said it expects a $300-million hit this year from the health care overhaul, which aims to eventually cover millions of uninsured people but imposes a host of new rules on the managed care sector.

The insurer also said last month that it had already more than doubled the enrollment gains it expected in 2011 for national accounts that the health insurer administers for large employers.

WellPoint expects adjusted earnings per share for 2011 of $6.30, a forecast that analysts have labeled conservative. They expect, on average, earnings of $6.62 per share.

WHY IT MATTERS: WellPoint had medical membership of about 33.3 million people at the end of last year. It runs Blue Cross Blue Shield plans in 14 states, including California, New York and Ohio. The company also is the second-largest insurer based on revenue, trailing only UnitedHealth.

WHAT'S EXPECTED: Analysts polled by FactSet expect, on average, earnings of $1.89 per share on $14.64 billion in revenue.

LAST YEAR'S QUARTER: WellPoint's profit climbed 51 percent in the first quarter of 2010 to $876.8 million, or $1.96 per share. But total revenue slipped to $15.1 billion from $15.14 billion. The company said it was helped in part by a gain of between $35 million and $50 million due to a weak flu season and improvements in parts of its enrollment, although total membership fell 2 percent to 33.8 million.