Health insurer Cigna Corp. reports first-quarter results Thursday before the market opens.

WHAT TO WATCH FOR: The Philadelphia company will become the last of the five largest health insurers to report first-quarter numbers, and it will face a high standard set by its competitors. UnitedHealth Group Inc., WellPoint Inc., Aetna Inc. and Humana Inc. have already reported earnings that beat Wall Street expectations and raised their 2011 forecasts.

They've been helped by enrollment gains, health care use that continues to rise slower than insurers expect and winter storms that kept people away from the doctor's office over the winter.

Insurers also have shown nervous investors that they can grow earnings despite a new health care overhaul rule that started this year and requires them to spend certain percentages of the premiums they collect on medical care or quality improvements.

UnitedHealth, WellPoint, Aetna and Humana all have started new quarterly dividends that significantly increased their payments to shareholders after piling up cash in recent quarters. Cigna, however, has strayed from that trend. It declared an annual dividend of 4 cents in February.

Cigna has a broader product portfolio than some of its competitors, so its performance can be affected by factors they don't face. It operates health care, group disability and life segments in the U.S. The insurer also has an international segment that sells individual insurance in several countries and operates an expatriate business that covers people living outside their home countries. Earnings from that segment grew 33 percent last year.

Cigna's performance also can be affected by its guaranteed minimum income benefits and variable annuity death benefits businesses. Cigna discontinued both in 2000 and operates them in run-off mode, meaning it seeks no new business. Those businesses hurt the company's performance when the market turns bad because Cigna's liabilities toward them increase.

Cigna also may see less of a gain from the slower-than-expected cost growth that has helped other insurers. That mostly benefits Cigna's customers because much of its medical enrollment involves employer-sponsored coverage it administers while the employer pays claims.

WHY IT MATTERS: Cigna is the fourth-largest commercial health insurer based on enrollment, trailing WellPoint, UnitedHealth and Aetna Inc.

WHAT'S EXPECTED: Analysts polled by FactSet expect, on average, earnings of $1.09 per share on $5.49 billion in revenue.

LAST YEAR'S QUARTER: Cigna started 2010 with a 36 percent jump in first-quarter profit. It earned $283 million, or $1.02 per share, and revenue rose 9 percent to $5.21 billion. Flu-related losses came in lower than the company expected, stabilizing enrollment helped premiums, and the insurer's international business saw earnings jump 76 percent in the quarter to $72 million.